refactor: unify user and user_preferences modules

[Panaetius]

moves user_preferences over to users namespace.
Also moves table to users schema, migrating old preferences and deleting the user_preferences db schema.

part of addressing #304

[Panaetius]

This change is part of the following stack:

• test: fix schemathesis query parameters test #340
  • refactor: unify user and user_preferences modules #325 ◀
    • refactor: add validation to crc, user and secrets endpoints #326

_{Change managed by git-spice.}

The base branch was changed.

[coveralls]

Pull Request Test Coverage Report for Build 10284691819

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 154 of 160 (96.25%) changed or added relevant lines in 9 files are covered.
• 5 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.07%) to 90.398%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
components/renku_data_services/users/db.py	54	56	96.43%
components/renku_data_services/migrations/versions/17eea03f938e_move_user_preferences_to_user_schema.py	23	27	85.19%

Files with Coverage Reduction	New Missed Lines	%
components/renku_data_services/base_api/auth.py	1	89.61%
components/renku_data_services/crc/blueprints.py	1	93.63%
components/renku_data_services/crc/models.py	1	84.91%
components/renku_data_services/crc/db.py	2	87.58%

Totals
Change from base Build 10282377659:	-0.07%
Covered Lines:	9038
Relevant Lines:	9998

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💛 - Coveralls