Add SetTag endpoint

[jescalada]

PR for adding the SetTag endpoint. I also added the DeleteTag endpoint from #8.

There are various new tests, all of which are passing except one:

• PASSING: test_set_tag_with_empty_string_as_value[sqlalchemy]
• PASSING: test_set_tag_validation[sqlalchemy]
• PASSING: test_set_tag_truncate_too_long_tag
• PASSING: test_update_run_name
• PASSING: test_update_run_name_without_changing_status[sqlalchemy]
• FAILING: test_set_tag

The reason why test_set_tag is failing, is that it uses monkeypatch to set an env, which doesn't flow to the Go side in our implementation. I have temporarily disabled that specific test by adding it to conftest.py until we can find a solution for similar tests.

I also added a test:PythonSpecific command for testing a single endpoint at a time.

[jescalada]

Looks like I messed up the line endings, will fix in a sec!

[dsuhinin]

It feels like you need to re generate mocks.

[jescalada]

I managed to get the test_set_tag_validation test to pass, however, I did this via a manual check in /pkg/tracking/service/tags.go. I also added the custom validator for the runId, however I am not sure how to integrate this with the existing code.

Is this meant to be used in our own Go tests? I noticed that for the LogBatch we're doing custom tests in /pkg/validation/validation_test.go.

[nojaf]

Oh and please rebase on latest main.