Dynamic client registration should be optional

[localden]

Currently getting this error if the target MCP server uses auth but does not provide dynamic client registration capabilities:

Per spec:

MCP clients and servers SHOULD support the OAuth 2.0 Dynamic Client Registration Protocol to allow MCP clients to obtain OAuth client IDs without user interaction. This provides a standardized way for clients to automatically register with new servers, which is crucial for MCP because:

• Clients cannot know all possible servers in advance
• Manual registration would create friction for users
• It enables seamless connection to new servers
• Servers can implement their own registration policies

Any MCP servers that do not support Dynamic Client Registration need to provide alternative ways to obtain a client ID (and, if applicable, client secret). For one of these servers, MCP clients will have to either:

1. Hardcode a client ID (and, if applicable, client secret) specifically for that MCP server, or
2. Present a UI to users that allows them to enter these details, after registering an OAuth client themselves (e.g., through a configuration interface hosted by the server).

There probably should be some graceful degradation here, or:

1. Assuming that the server will handle client assignment (e.g., in public client cases), -OR-
2. Provide some avenue to request a client ID.