[DOP-21268] - integration with SSO (Keycloak)

[maxim-lixakov]

Change Summary

• Implemented KeycloakAuthProvider for Single Sign-On (SSO) authentication.
• Implemented DummyAuthProvider for development and testing environments.
• Enabled dynamic selection of authentication provider via environment variable SYNCMASTER__AUTH__PROVIDER:

 # syncmaster.backend.providers.auth.keycloak_provider.KeycloakAuthProvider for Keycloak.
 SYNCMASTER__AUTH__PROVIDER=syncmaster.backend.providers.auth.keycloak_provider.KeycloakAuthProvider

  # syncmaster.backend.providers.auth.dummy_provider.DummyAuthProvider for Dummy authentication.
  SYNCMASTER__AUTH__PROVIDER=syncmaster.backend.providers.auth.dummy_provider.DummyAuthProvider

• Updated User model to include email, first_name, middle_name, and last_name fields.
• split Settings into SyncmasterSettings, WorkerSettings(SyncmasterSettings), BackendSettings(SyncmasterSettings)
• add KeycloakAuthProvider and DummyAuthProvider docs

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[codecov]

Codecov Report

Attention: Patch coverage is 67.44868% with 111 lines in your changes missing coverage. Please review.

Project coverage is 85.73%. Comparing base (af13e94) to head (4748ad7).
Report is 77 commits behind head on develop.

Files with missing lines	Patch %	Lines
...master/backend/providers/auth/keycloak_provider.py	28.20%	56 Missing ⚠️
...yncmaster/backend/providers/auth/dummy_provider.py	62.06%	22 Missing ⚠️
syncmaster/backend/api/v1/auth.py	64.00%	9 Missing ⚠️
...yncmaster/backend/dependencies/get_access_token.py	37.50%	5 Missing ⚠️
syncmaster/backend/utils/jwt.py	66.66%	3 Missing and 1 partial ⚠️
syncmaster/backend/utils/state.py	50.00%	4 Missing ⚠️
syncmaster/worker/transfer.py	0.00%	4 Missing ⚠️
syncmaster/backend/handler.py	77.77%	1 Missing and 1 partial ⚠️
syncmaster/backend/services/get_user.py	90.47%	1 Missing and 1 partial ⚠️
syncmaster/backend/middlewares/__init__.py	80.00%	0 Missing and 1 partial ⚠️
... and 2 more

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #123      +/-   ##
===========================================
- Coverage    87.52%   85.73%   -1.80%     
===========================================
  Files          143      157      +14     
  Lines         3342     3560     +218     
  Branches       251      261      +10     
===========================================
+ Hits          2925     3052     +127     
- Misses         355      444      +89     
- Partials        62       64       +2     

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