RFC 9728 Protected Resource Metadata plug.
The plug reads this value from the running server's :protected_resource
option and serves it on the MCP resource's own origin. Mount it separately at
the path-derived root route when Phoenix forwards the MCP app under /mcp;
that forward cannot receive /.well-known/... requests. A direct Plug mount
may still provide the value explicitly. Unconfigured routes return 404.
Summary
Functions
Runs the main entrypoint for this module.
Builds a child specification for supervising this module.
Initializes the state used by this module before it starts processing work.