Add support for secret scanning custom patterns

[stevehipwell]

GitHub has just announced support for managing secret scanning custom patterns via the REST API.

[gmlewis]

Thank you, @stevehipwell!

This would be a great PR for any new contributor to this repo or a new Go developer.
All contributions are greatly appreciated!

Feel free to volunteer for any issue and the issue can be assigned to you so that others don't attempt to duplicate the work.
Also feel free to perform a code review on any PR that has the label "NeedsReview" - we appreciate those contributions too!
We have a REVIEWERS file that you could add your username to if you are willing to be contacted when reviews are needed.

Please check out our CONTRIBUTING.md guide to get started. (In particular, please remember to go generate ./... and don't use force-push to your PRs.)

Thank you!

[tanayarun]

I'd like to work on this. I will ll look at the new custom patterns endpoints (list/create/get/update/delete) at the org and repo level and add corresponding methods + structs to SecretScanningService, according to the existing patterns in secret_scanning.go.
should this also cover enterprise level custom pattern endpoints if github exposes them, or keep this issue scoped to org/repo level only?

[gmlewis]

I'd like to work on this. I will ll look at the new custom patterns endpoints (list/create/get/update/delete) at the org and repo level and add corresponding methods + structs to SecretScanningService, according to the existing patterns in secret_scanning.go. should this also cover enterprise level custom pattern endpoints if github exposes them, or keep this issue scoped to org/repo level only?

The announcement says:

These endpoints are available at repository, organization, and enterprise levels for secret scanning customers.

So you could do one big PR or three smaller PRs (preferred) to fully resolve this issue.

Thank you, @tanayarun in advance! We appreciate your help.

[tanayarun]

Hey @gmlewis, thanks for assigning this to me, I am working on it right now, will raise a pr asap.