Support Oauth authentication

### Is there an existing issue that is already proposing this? - [x] I have searched the existing issues ### Application Outline Client ### What are you trying to do? What is your use case? ### Describe the solution you'd like. It would be great if the client could authenticate over OAuth with the server. That could allow us to trigger many different flows with a shared URL, like: - Sign up flow - Payment flow - Captcha - Show terms of service/privacy policy - Show ads - Show news/info It's not clear to me what the best practices are. MCP has mechanisms for OAuth discover: perhaps we can borrow from it - https://modelcontextprotocol.io/specification/2025-03-26/basic/authorization#example-authorization-code-grant - https://www.npmjs.com/package/mcp-remote - http://datatracker.ietf.org/doc/html/rfc7591 Example discovery metadata: https://radar.mcp.cloudflare.com/.well-known/oauth-authorization-server But there are default locations if the server doesn't support metadata.