GOATS-735: Extend login to save GPP credentials.

[davner]

• Add gpp_client library to communicate with GPP.
• Overhaul tests with ruff.

Jira Ticket: GOATS-735

Checklist

• Added or reviewed a release note in doc/changes.

[codecov]

Codecov Report

❌ Patch coverage is 91.70984% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.15%. Comparing base (50dcb8b) to head (2611645).
⚠️ Report is 94 commits behind head on main.

Files with missing lines	Patch %	Lines
src/goats_tom/views/logins/gpp.py	60.86%	9 Missing ⚠️
src/goats_tom/views/logins/base.py	86.66%	1 Missing and 1 partial ⚠️
src/goats_tom/tests/factories/reduceddatum.py	0.00%	1 Missing ⚠️
src/goats_tom/views/logins/astro_datalab.py	66.66%	1 Missing ⚠️
src/goats_tom/views/logins/goa.py	66.66%	1 Missing ⚠️
...oats_tom/processors/test_spectroscopy_processor.py	80.00%	1 Missing ⚠️
tests/goats_tom/tns/test_client.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #330      +/-   ##
==========================================
+ Coverage   72.83%   74.15%   +1.32%     
==========================================
  Files         219      203      -16     
  Lines        6604     6687      +83     
  Branches      448      455       +7     
==========================================
+ Hits         4810     4959     +149     
+ Misses       1717     1643      -74     
- Partials       77       85       +8     

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