134 test migrations

[filo14]

closes #134

This is not the most performant solution (schema.rs file is (un)stashed 2 times, docker image built 2 times), but as to not change the structure and existing functions of the Jenkinsfile too much, I did it this way. Performance and structure improvement for Jenkinsfile I see more in #241.

Basics

• [x] The PR is rebased with current master
• [x] I added a line to changelog.md
• [x] Details of what I changed are in the commit messages
• [x] References to issues, e.g. close #X, are in the commit messages and changelog
• [x] The buildserver is happy

Checklist

• [ ] I fully described what my PR does in the documentation
• [ ] I fixed all affected documentation
• [ ] I fixed the introduction tour
• [ ] I wrote migrations in a way that they are compatible with already present data
• [ ] I fixed all affected decisions
• [ ] I added automated tests or a manual test protocol
• [ ] I added code comments, logging, and assertions as appropriate
• [ ] I translated all strings visible to the user
• [ ] I mentioned every code or binary not directly written or done by me in reuse syntax
• [ ] I created left-over issues for things that are still to be done
• [ ] Code is conforming to our Architecture
• [ ] Code is conforming to our Guidelines
• [ ] Code is consistent to our Design Decisions
• [ ] Exceptions to any guidelines are documented

First Time Checklist

• [ ] I have installed and I am using pre-commit hooks
• [ ] I am using Tailwind CSS Linting

Review

• [ ] I've tested the code
• [ ] I've read through the whole code
• [ ] I've read through the whole documentation
• [ ] I've checked conformity to guidelines
• [ ] I've checked conformity to requirements
• [ ] I've checked that the requirements are tested