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

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