[DOP-19896] Add Clickhouse API schema

[IlyasDevelopment]

Change Summary

• Added Pydantic schemas for Clickhouse connection
• Added Pydantic schemas for Clickhouse source parameters and target parameters
• Added unit tests for creating & updating Clickhouse connection and target
• Updated README to include references to Clickhouse

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

All modified and coverable lines are covered by tests ✅

Project coverage is 87.26%. Comparing base (2260466) to head (088c880).
Report is 80 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #124      +/-   ##
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+ Coverage    87.12%   87.26%   +0.13%     
===========================================
  Files          140      141       +1     
  Lines         3240     3274      +34     
  Branches       251      251              
===========================================
+ Hits          2823     2857      +34     
  Misses         355      355              
  Partials        62       62              

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