Add twitter metadata and restructure the whole metadata part

- Remove duplications and don't require a specific file for every
subtype
- Add specific Twitter metadata since this is probably what is used most
for our users
- Use PNG logo since SVG is e.g. not supported by Twitter
- Add specific excerpts where not available yet

CONTRIBUTING.md

 ---
 layout: default
 title: Contribution Guide
+excerpt:
+  Contribution guide for the HIFIS Software website.
 ---
 # Contribution Guide
 

_config.yml

 # Global website configuration
 baseurl: ""
 
+url: https://software.hifis.net
+
 # Encoding needs to be UTF-8.
 encoding: utf-8
 

_includes/open_graph_protocol.html → _includes/metadata.html

@@ -5,44 +5,17 @@ Layout variable is passed from layout html file via top html file into
 open_graph_protocol html file.
 {% endcomment %}
 
-{% assign hifis_acronym = 'HIFIS - Helmholtz Federated IT Services - Software Services' %}
+{% assign hifis_acronym = 'HIFIS - Helmholtz Federated IT Services' %}
 
-{% include open_graph/og_all.html %}
+{% include metadata/all.html %}
 
 {% case include.layout | downcase %}
 
-{% when 'default' %}
-{% include open_graph/og_default.html %}
-
-{% when 'frontpage' %}
-{% include open_graph/og_frontpage.html %}
-
-{% when 'services' %}
-{% include open_graph/og_services.html %}
-
-{% when 'pagination' %}
-{% include open_graph/og_pagination.html %}
-
 {% when 'blogpost' %}
-{% include open_graph/og_blogpost.html %}
-
-{% when 'event-list' %}
-{% include open_graph/og_eventlist.html %}
-
-{% when 'event' %}
-{% include open_graph/og_event.html %}
-
-{% when 'team' %}
-{% include open_graph/og_team.html %}
-
-{% when 'member' %}
-{% include open_graph/og_member.html %}
+{% include metadata/blogpost.html %}
 
 {% else %}
-<!--
-    Warning: Open Graph was included, but the layout was not recognized.
-    Supported layouts are: 'default', 'frontpage', 'services', 'pagination',
-    'blogpost', 'event', 'event-list', 'team', 'member'.
--->
+
+{% include metadata/default.html %}
 
 {% endcase %}

_includes/metadata/all.html

+{% comment %}
+This file contains all open graph protocol metadata that is contained in every
+page.
+{% endcomment %}
+
+<meta property="twitter:card" content="summary_large_image" />
+<meta property="twitter:title" content="{{ page.title | strip_html }}" />
+<meta property="og:title" content="{{ page.title | strip_html }}" />
+<meta property="twitter:description" content="{{ page.excerpt | strip_html }}" />
+<meta property="og:description" content="{{ page.excerpt | strip_html }}" />
+<meta property="og:url" content="{{ site.url }}{{ page.url }}" />
+{% if page.title-image and page.title-image != 'default' %}
+{% assign image_url = site.directory.images | append: 'jumbotrons/desktop/' | append: page.title-image | absolute_url %}
+{% else %}
+{% assign image_url = site.directory.images | append: 'HIFIS_Logo_short_RGB.png' | absolute_url %}
+<meta property="og:image:alt" content="Logo of {{ hifis_acronym }}" />
+<meta property="twitter:image:alt" content="Logo of {{ hifis_acronym }}" />
+{% endif %}
+<meta property="twitter:image" content="{{ image_url }}" />
+<meta property="og:image" content="{{ image_url }}" />
+<meta property="og:local" content="en_US" />
+<meta property="og:site_name" content="https://software.hifis.net" />

_includes/open_graph/og_blogpost.html → _includes/metadata/blogpost.html

@@ -4,12 +4,6 @@ Instead of the id of the team member the full name is retrieved and
 added as author name of the blog post.
 {% endcomment %}
 
-<meta   property="og:title"
-        content="HIFIS Software Services - Blog Post '{{ page.title }}'" />
-
-<meta   property="og:description"
-        content="{{ page.excerpt | strip_html }}" />
-
 <meta   property="og:type" 
         content="article" />
 
@@ -21,7 +15,7 @@ added as author name of the blog post.
     {% assign person = person_entry[0] %}
     {% if person.name %}
         <meta   property="article:author" 
-                content="{{ person.title }}{{ person.name }}" />
+                content="{{ person.name }}" />
     {% else %}
         <meta   property="article:author" 
                 content="{{ author_id }}" />
@@ -34,4 +28,4 @@ added as author name of the blog post.
 {% for tag in page.tags %}
     <meta   property="article:tag" 
             content="{{ tag }}" />
-{% endfor %}
\ No newline at end of file
+{% endfor %}

_includes/open_graph/og_default.html → _includes/metadata/default.html

 {% comment %}
 This is open graph protocol metadata for pages with no or default layout.
 {% endcomment %}
+<meta property="og:type" content="website" />

_includes/open_graph/og_all.html

-{% comment %}
-This file contains all open graph protocol metadata that is contained in every
-page.
-{% endcomment %}
-
-<meta property="og:url" content="{{ site.url }}{{ page.url }}" />
-<meta property="og:image"
-      content="{{ site.url }}{{ site.directory.images }}HIFIS_Logo_short_RGB.svg" />
-<meta property="og:image:type" content="image/svg+xml" />
-<meta property="og:image:alt"
-      content="Logo of platform {{ hifis_acronym }}" />
-<meta property="og:image:width" content="294" />
-<meta property="og:image:height" content="100" />
-<meta property="og:local" content="en_US" />
-<meta property="og:site_name" content="https://software.hifis.net" />

_includes/open_graph/og_event.html

-{% comment %}
-This is open graph protocol metadata for event page layout.
-{% endcomment %}
-
-<meta property="og:title"
-      content="HIFIS Software Services - Event '{{ page.title }}'" />
-<meta property="og:description"
-      content="{{ hifis_acronym }}: {{ page.excerpt | strip_html }}" />
-<meta property="og:type" content="website" />

_includes/open_graph/og_eventlist.html

-{% comment %}
-This is open graph protocol metadata for event-list page layout.
-{% endcomment %}
-
-<meta property="og:title"
-      content="HIFIS Software Services - Events Overview" />
-<meta property="og:description"
-      content="{{ hifis_acronym }}: Events Overview." />
-<meta property="og:type" content="website" />

_includes/open_graph/og_frontpage.html

-{% comment %}
-This is open graph protocol metadata for front page layout.
-{% endcomment %}
-
-<meta property="og:title"
-      content="HIFIS Software Services - Website" />
-<meta property="og:description"
-      content="{{ hifis_acronym }}: Website." />
-<meta property="og:type" content="website" />

_includes/open_graph/og_member.html

-{% comment %}
-This is open graph protocol metadata for member page layout.
-{% endcomment %}
-
-<meta property="og:title"
-      content="HIFIS Software Services - Team Member" />
-<meta property="og:description"
-      content="{{ hifis_acronym }}: Team Member." />
-<meta property="og:type" content="website" />

_includes/open_graph/og_pagination.html

-{% comment %}
-This is open graph protocol metadata for blog post list page layout.
-{% endcomment %}
-
-<meta property="og:title"
-      content="HIFIS Software Services - Blog Posts Overview" />
-<meta property="og:description"
-      content="{{ hifis_acronym }}: Blog Posts Overview." />
-<meta property="og:type" content="website" />

_includes/open_graph/og_services.html

-{% comment %}
-This is open graph protocol metadata for services page layout.
-{% endcomment %}
-
-<meta property="og:title"
-      content="HIFIS Software Services - Services" />
-<meta property="og:description"
-      content="{{ hifis_acronym }}: Services Overview." />
-<meta property="og:type" content="website" />

_includes/open_graph/og_team.html

-{% comment %}
-This is open graph protocol metadata for team page layout.
-{% endcomment %}
-
-<meta property="og:title"
-      content="HIFIS Software Services - Team Members Overview" />
-<meta property="og:description"
-      content="{{ hifis_acronym }}: Team Members Overview." />
-<meta property="og:type" content="website" />

_includes/top.html

@@ -12,7 +12,8 @@
 <head>
     {% include minimal_head.html %}
 
-    {% include open_graph_protocol.html layout = page.layout %}
+    {% assign layout = page.layout | slugify %}
+    {% include metadata.html layout = layout %}
 
     {% comment %}
         Add in additional CSS if such is requested in the header of the

_posts/2019/10/2019-10-29-Blog-Post-Features.md

@@ -6,7 +6,6 @@ authors:
   - erxleben
 layout: blogpost
 title-image: default
-excerpt_separator: <!--more-->
 categories:
   - blog
 tags:
@@ -15,13 +14,15 @@ tags:
   - markdown
 additional_js:
   - mathjax.js
+excerpt:
+  This post will give you an overview of all the features you can use in your
+  very own HIFIS Software blog post.
 ---
 
 # Blog Post Metadata
 
 This post will give you an overview of all the features you can use in your
 very own HIFIS Software blog post.
-<!--more-->
 
 ## The Frontmatter
 

_posts/2019/11/2019-11-22-How-to-Create-a-new-Blog-Post.md

 ---
-title:  How to Create a New Blog Post?
-date:   2019-11-22
+title: How to Create a New Blog Post?
+date: 2019-11-22
 authors:
-    - hueser
+  - hueser
 layout: blogpost
-title-image:    default
-excerpt_separator: <!--more-->
+title-image: default
 categories: [tutorials]
 tags: [startblogging, guidedtour]
 additional_css:
-    - 2019-11-22-Workflow-to-Create-a-new-Blog-Post/create_blog_post.css
+  - 2019-11-22-Workflow-to-Create-a-new-Blog-Post/create_blog_post.css
+excerpt: 
+  Nice project web page, how can I contribute with my own blog post?
+  This is what this blog post is about.
+  I will explain the workflow of &ldquo;how to create a new blog post&rdquo; and
+  thereby illustrate how to use the tools Git, GitLab and Jekyll
+  for these purposes.
 ---
 
 ## TL;DR
@@ -20,7 +25,7 @@ This is what this blog post is about.
 I will explain the workflow of "how to create a new blog post" and 
 thereby illustrate how to use the tools _Git_, _GitLab_ and _Jekyll_
 for these purposes.
-<!--more-->
+
 There are minimal requirements for a blogger to add a new blog post
 while a proper review process is still essential for the quality of
 the blog posts.

events.md

@@ -2,9 +2,12 @@
 title: Events
 title-image: default
 layout: event-list
+excerpt:
+  "Upcoming and past events that are related to or organized by HIFIS
+  Software."
 ---
 ```
   This markdown file triggers the generation of the event-list page.
   Only the frontmatter is required by Jekyll.
   The contents section does not get rendered into HTML on purpose.
-```
\ No newline at end of file
+```

faq.md

 ---
 title: <i class="fas fa-question-circle"></i> FAQ - Frequently Asked Questions
 layout: default
+excerpt:
+    Collection of Frequently Asked Question (FAQ) about HIFIS Software.
 ---
 
 ## General