docs: update labels and restructure items for OAuth2 documentation

[christiannwamba]

Related Issue or Design Document

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact [email protected]) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

Further comments

[vinckr]

a bit on the fence on this change tbh - I am not sure if it doesn't muddy up the boundary between Ory Identities/Ory OAuth2. Especially if we go back to using more the OSS product names it's going to be confusing.

[vinckr]

maybe it's just me but I find this very unclear / have no idea what is in this category before I open it.

Wouldn't OIDC be the thing that everyone knows here?