Create interface for registering entity through Provider

[JAORMX]

Summary

This is an interface that ensures that the provider does the necessary
steps to ensure Minder can track an entity. For GitHub and GitLab it
will be as a webhook for the repo or project. In DockerHub it'll be
a webhook for the image repository. Other providers might have other
steps.

The purpose is to define the interface, not implement it. That'll happen
in another PR.

Closes: #4325

Change Type

Mark the type of change your PR introduces:

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

Outline how the changes were tested, including steps to reproduce and any relevant configurations.
Attach screenshots if helpful.

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[coveralls]

coverage: 52.67% (-0.1%) from 52.815%
when pulling 41f7fe2 on register-interface
into 1a5c09e on main.