Add CIMD (Client ID Metadata Document) Helpers

[Avinash-Kamath]

Spec:

https://datatracker.ietf.org/doc/draft-ietf-oauth-client-id-metadata-document/

Why

MCP is becoming widely adopted and is beginning to prefer CIMD over Dynamic Client Registration (DCR). Adding CIMD helpers make it easier for devs connecting to CIMD servers

Current Way of doing this

Create Oauth2 config. Create a struct with CIMD fields convert to json in the http handler and return the metadata to the server. Acknowledging that this works fine

Proposed Changes

Helper to generate CIMD metadata
A function that produces a CIMD metadata struct/document from the existing OAuth config.

Helper to register a CIMD endpoint
A function that takes an HTTP handler/router, a path, and OAuth client config, and registers an endpoint that returns CIMD-compliant metadata.

Happy to contribute the implementation if this feature is accepted.