Feat: Custom Delegation Roles API endpoints

[kairoaraujo]

Description

Add endpoints to support Custom Delegation Roles.

It is related:

1. feat: Custom Delegation(Target) Roles repository-service-tuf-worker#592
2. FT: Custom Delegation Roles repository-service-tuf#817

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)

Additional requirements

• [~] Tests have been added for the bug fix or new feature
• Docs have been added for the bug fix or new feature

Code of Conduct

By submitting this PR, you agree to follow our Code of Conduct.

• I agree to follow this project's Code of Conduct

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 30 lines in your changes missing coverage. Please review.

Project coverage is 94.45%. Comparing base (25928b7) to head (ab88455).
Report is 121 commits behind head on main.

Files with missing lines	Patch %	Lines
repository_service_tuf_api/metadata.py	66.66%	11 Missing ⚠️
repository_service_tuf_api/delegations.py	73.68%	10 Missing ⚠️
repository_service_tuf_api/common_models.py	66.66%	4 Missing ⚠️
repository_service_tuf_api/api/delegations.py	75.00%	3 Missing ⚠️
repository_service_tuf_api/bootstrap.py	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #688      +/-   ##
==========================================
- Coverage   98.97%   94.45%   -4.53%     
==========================================
  Files          14       16       +2     
  Lines         588      758     +170     
==========================================
+ Hits          582      716     +134     
- Misses          6       42      +36     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[kairoaraujo]

Supressed by #689 that shows FT.