Add check source has tests by group

[ashleemtib]

Solution for issue: #75

Added check_source_has_tests_by_group.py for a new hook that checks if a source has one or more tests within a test group. This hook enables searching of multiple types of tests on sources using OR logic, where any of the tests configured in the .yaml will cause the pre-commit check to pass.

This can be configured in the .pre-commit-config.yaml like so:

    - id: check-source-has-tests-by-group
      args: ["--manifest", "dbt/target/manifest.json", "--tests", "unique", "unique_where", "unique_combination_of_columns", "--test-cnt", "1", "--"]
      name: check-source-has-tests-by-group
      verbose: true    

We tested this by running pre-commit run check-source-has-tests-by-group on a source with no uniqueness tests which proved failures, and then added a unique combination of columns test to the same source to prove passing.

[ashleemtib]

Currently unsure how to interpret the pytest failures.

[eve-johns]

I think we need to also write a test file for this.

[ashleemtib]

Hi @ssassi, could you help us move this one along?

[ssassi]

Thanks @ashleemtib. @BAntonellini will take a look.

[BAntonellini]

Been testing locally using different PASS and FAIL expectancies, and everything is correct

[katieclaiborne]

Thanks, Bruno and Sebastián!

Are you all planning to cut a new release for the package any time soon? We're updating the rev: key in our repository's .pre-commit-config.yaml file to point to this commit, but would love to have a stable tag to point to instead.