[#840] config: fix: Add dagsDir config key

[yohamta]

Issue: #840

Changes:

• Added dagsDir config key
• Added tests for config load
• Added todo for config refactor

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.62%. Comparing base (09a89c5) to head (91b1d9e).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #850      +/-   ##
==========================================
+ Coverage   55.48%   55.62%   +0.14%     
==========================================
  Files          75       75              
  Lines        8170     8174       +4     
==========================================
+ Hits         4533     4547      +14     
+ Misses       3241     3227      -14     
- Partials      396      400       +4     

Files with missing lines	Coverage Δ
internal/config/config.go	80.80% <100.00%> (+11.01%)	⬆️
internal/config/loader.go	78.20% <100.00%> (+0.09%)	⬆️

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