Add PropsDB overrides

[oschulz]

Override data locations are

/path/to/metadata/jldataprod/overrides/metadata/...
/path/to/metadata/jldataprod/overrides/par/...
/path/to/metadata/jldataprod/overrides/jlpar/...

@theHenks can you test if this PR works for you?

[codecov]

Codecov Report

Attention: Patch coverage is 52.52525% with 47 lines in your changes missing coverage. Please review.

Project coverage is 33.25%. Comparing base (469a00e) to head (d9483fa).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/props_db.jl	50.54%	45 Missing ⚠️
src/legend_data.jl	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #62      +/-   ##
==========================================
+ Coverage   33.00%   33.25%   +0.25%     
==========================================
  Files          27       27              
  Lines        1618     1690      +72     
==========================================
+ Hits          534      562      +28     
- Misses       1084     1128      +44     

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[oschulz]

I'll merge this, we can always improved it some more later.