Cue-based assignment description format

[meling]

This provides a first draft of a Cue-based assignment description format that can replace assignment.yml files and provide more robust checks.

[ghost]

Review on Crocodile

[codecov-commenter]

Codecov Report

Merging #676 (ba23236) into master (8b1b67e) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #676      +/-   ##
==========================================
- Coverage   23.07%   23.00%   -0.07%     
==========================================
  Files          65       65              
  Lines       10181    10181              
==========================================
- Hits         2349     2342       -7     
- Misses       7507     7512       +5     
- Partials      325      327       +2     

Flag	Coverage Δ
unittests	23.00% <ø> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
web/rebuild.go	64.36% <0.00%> (-8.05%)	⬇️

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[coveralls]

Pull Request Test Coverage Report for Build 2627690856

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 25.617%

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Totals
Change from base Build 2625705654:	0.0%
Covered Lines:	2710
Relevant Lines:	10579

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💛 - Coveralls