fix: make it able to expand project env vars in dotenv file

[frostming]

Signed-off-by: Frost Ming [email protected]

Close #2993

Pull Request Checklist

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Describe what you have changed in this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.64%. Comparing base (c889ae1) to head (ed5bad7).
Report is 90 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3087      +/-   ##
==========================================
- Coverage   85.65%   85.64%   -0.01%     
==========================================
  Files         109      109              
  Lines       10957    10957              
  Branches     2394     2393       -1     
==========================================
- Hits         9385     9384       -1     
  Misses       1086     1086              
- Partials      486      487       +1     

Flag	Coverage Δ
unittests	85.44% <100.00%> (-0.01%)	⬇️

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