handle GET reqs with invalid query params as 400

[adysenrothman]

Description

Currently, when an user inputs a request with a query param that has an invalid syntax issue, it gets processed as a 500 internal service error. We should be processing these as a 400 bad request instead.

Link to original Jira with more details: https://issues.redhat.com/browse/RHOAIENG-19195

How Has This Been Tested?

This has been locally tested by creating new registered models and model artifacts, and then sending GET requests with bad query params for name and externalId in order to trigger the "Illegal syntax" error. For example:
GET /api/model_registry/v1alpha3/registered_model?%C3%B5%F1%A5%BC%A2x%1D%1C&externalId=1l%26%F3%AF%81%9Fd%F0%96%B0%AD%5C-%10%C3%AD%09%C3%BD%F3%BF%B9%B0%C2%98%C3%8B%C3%A7%F0%BF%BD%A4%3D%C2%BB%C2%B0%C3%AF

Merge criteria:

• All the commits have been signed-off (To pass the DCO check)

• [x ] The commits have meaningful messages; the author will squash them after approval or in case of manual merges will ask to merge with squash.
• [x ] Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• [x ] The developer has manually tested the changes and verified that the changes work.
• [ x] Code changes follow the kubeflow contribution guidelines.

[google-oss-prow]

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[rareddy]

any unit test case?

[adysenrothman]

any unit test case?

yes, just added several tests to catch these 400 errors @rareddy

[rareddy]

/lgtm