Generate variable catalogs for each variable in the dataset

[TejasMorbagal]

This PR implements variable STAC catalog generation for each variable in the dataset.

Note that 'gcmd_keyword_url' is expected as variable metadata if the variable in the dataset doesn't have a corresponding catalog already in OSC.

[codecov]

Codecov Report

Attention: Patch coverage is 55.55556% with 44 lines in your changes missing coverage. Please review.

Project coverage is 86.36%. Comparing base (c363d08) to head (c9ee5ad).

Files with missing lines	Patch %	Lines
deep_code/utils/dataset_stac_generator.py	48.27%	30 Missing ⚠️
deep_code/tools/publish.py	62.50%	9 Missing ⚠️
deep_code/utils/github_automation.py	20.00%	4 Missing ⚠️
deep_code/cli/publish.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #2      +/-   ##
==========================================
- Coverage   90.82%   86.36%   -4.46%     
==========================================
  Files          13       13              
  Lines         665      719      +54     
==========================================
+ Hits          604      621      +17     
- Misses         61       98      +37     

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