Add submodule strategy to .gitlab-ci.yml

2 jobs for main in 40 seconds (queued for 20 seconds)
Name Stage Failure
build-testar-api Build Testar Api
[ERROR] -> [Help 1]
[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