Add send payload for ceremony, metadata update and sign

[MVrachev]

Note: Review and merge after merging #612

Description

Add send payload for ceremony, metadata update and sign.

Related to: #533

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

[MVrachev]

I had problems running locally plantuml.
@kairoaraujo could you please run it locally and update especially https://github.com/repository-service-tuf/repository-service-tuf-cli/blob/main/docs/source/_static/repository-service-tuf-cli-C3.png diagram as I made changes there.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.96%. Comparing base (47d0a69) to head (6edd6ec).
Report is 97 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #620      +/-   ##
==========================================
+ Coverage   98.90%   98.96%   +0.06%     
==========================================
  Files          20       30      +10     
  Lines        1367     1931     +564     
==========================================
+ Hits         1352     1911     +559     
- Misses         15       20       +5     

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[MVrachev]

The changes from pr #612 pr are part of this pr.
Commits from Make "--api-server" an admin option up to Fix unit tests were all part of #612 and are discussed there, but due to mistake we merged this pr first.