Update to_df to include metadata

[WeilerP]

Changes

• Adds argument obs to include columns from .obs in generated metadata.

Related issues

Closes #1399.

[WeilerP]

I'll add unit tests once it's clear if this feature is desired and how to include it.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 84.19%. Comparing base (9452dd5) to head (fa07b95).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1400      +/-   ##
==========================================
- Coverage   86.27%   84.19%   -2.08%     
==========================================
  Files          36       36              
  Lines        5610     5613       +3     
==========================================
- Hits         4840     4726     -114     
- Misses        770      887     +117     

Flag	Coverage Δ
gpu-tests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
anndata/_core/anndata.py	84.76% <80.00%> (-0.07%)	⬇️

... and 8 files with indirect coverage changes

[ivirshup]

Just to write down some edge cases:

• What if there are repeated:
  • obs_names
  • var_names
• What if (key in adata.obs.columns) and (key in adata.var_names)