OAuth2 Authorization endpoint for Authorization Code flow

OAuth2 Authorization endpoint that initiates the Authorization Code flow.

This endpoint should be accessed by the user's browser to authorize a third-party application.

Required parameters:

• response_type: Must be 'code' for Authorization Code flow
• client_id: The OAuth2 client identifier
• redirect_uri: Where to redirect after authorization (must be registered with the client)
• scope: Space-separated list of requested permissions (optional)
• state: Random string to prevent CSRF attacks (optional)

Example:

GET /api/v1/auth/oauth2/authorize?response_type=code&client_id=123&redirect_uri=https://example.com/callback&scope=read write&state=xyz123

The user will be redirected to a login page if not authenticated, then to a consent page, and finally back to the redirect_uri with an authorization code.