Update the Auth Service api docs and deprecations

[DenysVuika]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation
• Other... Please describe:

What is the current behaviour? (You can also link to an open issue here)

What is the new behaviour?

• remove unused api (verified with all apps)
• better documenting of the deprecated apis
• cleanup docs and remove missing api

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[sonarcloud]

Quality Gate failed

Failed conditions
5.5% Duplication on New Code (required ≤ 3%)
C Maintainability Rating on New Code (required ≥ A)

See analysis details on SonarCloud

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[alep85]

@DenysVuika it looks good to me, did you raise a PR on hxp-frontend-apps linking this branch? Just to be sure that all tests pass