Add before field (Breaking)

[fernando79513]

Description

This PR adds a new field called "before" to the jobs. This field allows a new type of dependency for the jobs.
The way the dependency manager sorts the jobs has not changed. Instead, the way the before flag works is by adding the current job as an after dependency of the jobs listed in the before field.

These references are added to the job object as a new attribute and included to the after_deps set when retrieving the dependency set.

Resolved issues

https://warthogs.atlassian.net/browse/CHECKBOX-1919

Documentation

The "before" flag has also been added to the corresponding section in the checkbox documentation.

Tests

Unit tests for this feature have been added In the PR

[codecov]

Codecov Report

❌ Patch coverage is 90.29126% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.56%. Comparing base (42842da) to head (569dcd5).
⚠️ Report is 125 commits behind head on main.

Files with missing lines	Patch %	Lines
checkbox-ng/plainbox/impl/depmgr.py	88.88%	5 Missing and 3 partials ⚠️
checkbox-ng/plainbox/impl/unit/job.py	88.23%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1935      +/-   ##
==========================================
+ Coverage   50.40%   50.56%   +0.16%     
==========================================
  Files         384      384              
  Lines       41087    41169      +82     
  Branches     6749     7421     +672     
==========================================
+ Hits        20709    20817     +108     
+ Misses      19637    19605      -32     
- Partials      741      747       +6     

Flag	Coverage Δ
checkbox-ng	70.32% <90.29%> (+0.29%)	⬆️

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[pieqq]

I tested it locally by butchering jobs in the client-cert-desktop-24-04-automated test plan and seeing what was happening, and it works as expected in my quick test.

If possible, add more warnings in the documentation about this field.

[Hook25]

See below, please consider not failing on missing job

[pieqq]

two little suggestions

[Hook25]

+1, wait for @pieqq to give a look as well but this looks good to me. Adjusting the title, this is a breaking change!

[pieqq]

I left some inline comments regarding the documentation. It would be good if you took a look at it, but otherwise I think the feature works as expected.

I've done the following test, since we have an issue with debsum being run after a wireless test that modifies netplan config:

1. Moved the misc-client-cert-automated nested part in the client-cert-desktop-24-04-automated test plan to the very end. This nested part includes miscellanea/debsums.
2. Ran checkbox-cli list-bootstrapped "com.canonical.certification::client-cert-desktop-24-04-automated" > /var/tmp/misc_np_at_the_end
3. Looked at the result, and indeed the jobs from that nested part are all towards the end, including the debsum job.
4. Edited the miscellanea/debsums job to add before: wireless/detect
5. Ran checkbox-cli list-bootstrapped "com.canonical.certification::client-cert-desktop-24-04-automated" > /var/tmp/misc_np_at_the_end_before_field_added

Compared the two, and sure enough, all the jobs from the misc-client-cert-automated nested part are still at the end of the list, except miscellanea/debsums which sits just before wireless/detect. (this should fix our problem, so it means the feature works great! :)