OP-15067: gate approval api

[ramyaravi-opsmx]

We prefer small, well tested pull requests.

Please refer to Contributing to Spinnaker.

When filling out a pull request, please consider the following:

• Follow the commit message conventions found here.
• Provide a descriptive summary for your changes.
• If it fixes a bug or resolves a feature request, be sure to link to that issue.
• Add inline code comments to changes that might not be obvious.
• Squash your commits as you keep adding changes.
• Add a comment to @spinnaker/reviewers for review if your issue has been outstanding for more than 3 days.

Note that we are unlikely to accept pull requests that add features without prior discussion. The best way to propose a feature is to open an issue first and discuss your ideas there before implementing them.

https://devopsmx.atlassian.net/browse/OP-15067

[opsmxuser]

This PR triggered this build in this execution, please wait for it and child pipelines to succeed before merging: https://isd.prod.opsmx.net/deck/#/applications/gcp-gitprtrigger/executions/details/01G2CR8K43RSRMN772Y05EC4EQ

[opsmxuser]

This PR triggered this build in this execution, please merge to master only if this succeeds: https://isd.prod.opsmx.net/deck/#/applications/gcp-gitprtrigger/executions/details/01G2CR8W1JZHVT6HBATKA8EF6D

[opsmxuser]

SUCCESSFUL RunTests RESULT: Tests run: 204, Failures: 2, Errors: 0, Skipped: 5, Time elapsed: 269.019 sec <<< FAILURE! Reviewers , this PR did not cause the failures in https://jenkins.opsmx.net:8181/jenkins/job/Dev-run-tests-on-gitpr-parallel/ws/emailable-report-40.html