Change accepted region code pattern and add documentation

* Region Codes need to be seperated by dashes.
* If lookup for region codes fail, the pure language code will be tried instead. If these also fail, an error is raised

Signed-off-by: Fredo Erxleben <f.erxleben@hzdr.de>
4 jobs for !112 with 126-accept-ietf-language-tags in 2 minutes and 23 seconds (queued for 7 seconds)
latest detached
Status Name Job ID Coverage
  Test
passed lint #328119

00:01:09

passed sqa:dev #328121
internal

00:00:33

passed test #328120

00:01:01

 
  Build
passed build:package #328122

00:01:14