Include resource field in OAuth authorization details response

[tdabasinskas]

Feature request

The OAuth authorization server accepts the resource parameter (RFC 8707) in the /oauth/authorize request and stores it on the FlowState, but the GET /oauth/authorizations/{id} endpoint does not include it in the AuthorizationDetailsResponse.

Problem

When building a consent page, we need to show the user which resource the client is requesting access to — not just the client name and scopes. The resource parameter carries this information (e.g., https://mcp-server.com), but since it's omitted from the authorization details response, the consent page has no way to display it.

The current response struct:

  type AuthorizationDetailsResponse struct {
      AuthorizationID string                `json:"authorization_id"`
      RedirectURI     string                `json:"redirect_uri,omitempty"`
      Client          ClientDetailsResponse `json:"client,omitempty"`
      User            UserDetailsResponse   `json:"user,omitempty"`
      Scope           string                `json:"scope,omitempty"`
  }

Proposed change

Add the resource field to AuthorizationDetailsResponse:

type AuthorizationDetailsResponse struct {
    AuthorizationID string                `json:"authorization_id"`
    RedirectURI     string                `json:"redirect_uri,omitempty"`
    Resource        string                `json:"resource,omitempty"`
    Client          ClientDetailsResponse `json:"client,omitempty"`
    User            UserDetailsResponse   `json:"user,omitempty"`
    Scope           string                `json:"scope,omitempty"`
}

And populate it from the stored authorization in OAuthServerGetAuthorization.

Context

This is relevant for MCP (Model Context Protocol) OAuth flows where tools like Cursor send resource=https://mc-server.com/ when authorizing. The consent page needs this to show the user which specific resource (e.g., which AI agent) the client is requesting access to, rather than displaying a generic "authorize this application" prompt.