docs: draft guidlines for authors of custom tests

[ChristianLieven]

• [X] fix #559
• [X] add entry to history.rst

I've tried drafting a set of guidelines for custom tests as per request from one of the reviewers. I'll add to this if I can think of more, but for now, let me know if you have any suggestions.

[codecov[bot]]

Codecov Report

Merging #623 into develop will not change coverage. The diff coverage is n/a.

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[codecov[bot]]

Codecov Report

Merging #623 into develop will not change coverage. The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #623   +/-   ##
========================================
  Coverage    80.03%   80.03%           
========================================
  Files           59       59           
  Lines         3131     3131           
  Branches       428      428           
========================================
  Hits          2506     2506           
  Misses         552      552           
  Partials        73       73

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update fec22ee...c79a0ed. Read the comment docs.

[ChristianLieven]

Point 4 and 5 seem a bit excessive - while in general good advice, is it really necessary for memote to reiterate this, or should these guidelines stick to memote- and modeling-related matters?

I think it is very important to state this cleary. If researchers will be submitting/ sharing their custom test cases, they should have an understanding of the programming standards/ code style we adhere to. These are only guidelines though, so it is still up to the individual to follow them or not.