CI pipeline for mysql unit tests

Summary

The pipeline should also run the tests with a MySQL as backend server. This MR implements this.

See also #33 (closed).

Focus

• Does the MySQL pipeline fail at the expected point?
• Is outsourcing pipeline code to a Makefile a reasonable step to prevent redundancy in the scripts?

Test Environment

Just watch the pipeline run.

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• All automated tests pass
• Reference related Issues
• Up-to-date CHANGELOG.md
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

For further good practices have a look at our review guidelines.

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added ###
 
+* #33 CI pipeline for MySQL (was only MariaDB before).
+
 ### Changed ###
 
 ### Deprecated ###