Fix attributes not merged

[puzzledpolymath]

🔍 What was changed

• Updated composer psalm version to support PHP 8.4
• Updated contributing instructions for running docker compose
• Added further unit tests proving an issue with merging attributes when a default value is defined
• Added a fix ensuring attributes are merged correctly
• General house cleaning in order to get pipelines working correctly

📝 Checklist

While this PR does not close a particular ticket. The issue was raised here: cycle/database#228

• How was this tested:
  • Unit tests added

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.86%. Comparing base (af4816c) to head (47e3c88).
Report is 11 commits behind head on 2.x.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x      #82      +/-   ##
============================================
- Coverage     94.86%   94.86%   -0.01%     
  Complexity      591      591              
============================================
  Files            45       45              
  Lines          1676     1675       -1     
============================================
- Hits           1590     1589       -1     
  Misses           86       86              

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[puzzledpolymath]

@roxblnfk Let me know if anything further is needed here. Ideally I'll like to see this merged and then move onto cycle/database#228, which I'll likely needed assistance with.