Add gitops app config fields, API access, activities, tests

[jacobshandling]

For #26230

• Add gitops settings to app config
• GET and PATCH endpoint functionality to retrieve and modify these settings
• generate activities for enabling and disabling GitOps mode
• Premium only
• Update tests

Checklist for submitter

• Added/updated automated tests
• A detailed QA plan exists on the associated ticket (if it isn't there, work with the product group's QA engineer to add it)
• Manual QA for all new/changed functionality

[codecov]

Codecov Report

Attention: Patch coverage is 86.36364% with 3 lines in your changes missing coverage. Please review.

Project coverage is 63.85%. Comparing base (403deb1) to head (b410347).
Report is 23 commits behind head on main.

Files with missing lines	Patch %	Lines
server/service/appconfig.go	86.36%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #26282      +/-   ##
==========================================
+ Coverage   63.72%   63.85%   +0.13%     
==========================================
  Files        1655     1656       +1     
  Lines      158544   159054     +510     
  Branches     4144     4125      -19     
==========================================
+ Hits       101032   101566     +534     
+ Misses      49587    49549      -38     
- Partials     7925     7939      +14     

Flag	Coverage Δ
backend	64.69% <86.36%> (+0.13%)	⬆️

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[dantecatalfamo]

Should just add a quick s.lastActivityOfTypeMatches to make sure the activity shows up when you enable gitops ui mode