Sentry Configuration

We need to allow users to configure Sentry integration with GitLab.

We should:

1. Add a Settings->Operations->Errors section
2. Have a short description of what this is, with a link to the documentation.
3. Allow users to enter the Sentry URL
4. Allow users to enter the Sentry Bearer token, with a (?) which links to the docs on how to get it.
5. Expose a Save button to persist these.

This should only be available for Maintainers