Add handler for resource templates

We missed to have a handler for resource templates. We add this
now. One caveat is still that the `uriTemplate` in `ResourceTemplate`
is not a pydantic type.

src/mcp/server/__init__.py

@@ -30,6 +30,10 @@ Usage:
    ) -> list[types.TextContent | types.ImageContent | types.EmbeddedResource]:
        # Implementation
 
+   @server.list_resource_templates()
+   async def handle_list_resource_templates() -> list[types.ResourceTemplate]:
+       # Implementation
+
 3. Define notification handlers if needed:
    @server.progress_notification()
    async def handle_progress(
@@ -227,6 +231,21 @@ class Server:
 
         return decorator
 
+    def list_resource_templates(self):
+        def decorator(func: Callable[[], Awaitable[list[types.ResourceTemplate]]]):
+            logger.debug("Registering handler for ListResourceTemplatesRequest")
+
+            async def handler(_: Any):
+                templates = await func()
+                return types.ServerResult(
+                    types.ListResourceTemplatesResult(resourceTemplates=templates)
+                )
+
+            self.request_handlers[types.ListResourceTemplatesRequest] = handler
+            return func
+
+        return decorator
+
     def read_resource(self):
         def decorator(func: Callable[[AnyUrl], Awaitable[str | bytes]]):
             logger.debug("Registering handler for ReadResourceRequest")