adapt build variables

5 jobs for master in 47 seconds (queued for 3 seconds)
Name Stage Failure
build Build
[ERROR]     'artifactId' with value 'helmholtz-marketplace-webapp.${env.WEBAPP_BRANCH}' does not match a valid id pattern. @ de.helmholtz.marketplace:helmholtz-marketplace-webapp.${env.WEBAPP_BRANCH}:${env.WEBAPP_PROJECT_VERSION}, /builds/hifis-technical-platform/helmholtz-marketplace-webapp/pom.xml, line 6, column 14
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1]
Cleaning up file based variables
ERROR: Job failed: exit code 1