feat: implement resource update notifications (#264)

This enables servers to notify clients when specific resources are updated,
allowing clients to react to individual resource changes rather than just
list changes.

- Add ResourcesUpdatedNotification schema with uri field
- Add METHOD_NOTIFICATION_RESOURCES_UPDATED constant
- Implement notifyResourcesUpdated() methods in McpAsyncServer and McpSyncServer
- Add client-side support for resource update consumers and handlers
- Client automatically reads updated resource content when notification received
- Add tests for both async and sync server implementations

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

mcp-test/src/main/java/io/modelcontextprotocol/server/AbstractMcpAsyncServerTests.java

@@ -194,6 +194,18 @@ public abstract class AbstractMcpAsyncServerTests {
 		assertThatCode(() -> mcpAsyncServer.closeGracefully().block(Duration.ofSeconds(10))).doesNotThrowAnyException();
 	}
 
+	@Test
+	void testNotifyResourcesUpdated() {
+		var mcpAsyncServer = McpServer.async(createMcpTransportProvider()).serverInfo("test-server", "1.0.0").build();
+
+		StepVerifier
+			.create(mcpAsyncServer
+				.notifyResourcesUpdated(new McpSchema.ResourcesUpdatedNotification(TEST_RESOURCE_URI)))
+			.verifyComplete();
+
+		assertThatCode(() -> mcpAsyncServer.closeGracefully().block(Duration.ofSeconds(10))).doesNotThrowAnyException();
+	}
+
 	@Test
 	void testAddResource() {
 		var mcpAsyncServer = McpServer.async(createMcpTransportProvider())

mcp-test/src/main/java/io/modelcontextprotocol/server/AbstractMcpSyncServerTests.java

@@ -191,6 +191,17 @@ public abstract class AbstractMcpSyncServerTests {
 		assertThatCode(() -> mcpSyncServer.closeGracefully()).doesNotThrowAnyException();
 	}
 
+	@Test
+	void testNotifyResourcesUpdated() {
+		var mcpSyncServer = McpServer.sync(createMcpTransportProvider()).serverInfo("test-server", "1.0.0").build();
+
+		assertThatCode(() -> mcpSyncServer
+			.notifyResourcesUpdated(new McpSchema.ResourcesUpdatedNotification(TEST_RESOURCE_URI)))
+			.doesNotThrowAnyException();
+
+		assertThatCode(() -> mcpSyncServer.closeGracefully()).doesNotThrowAnyException();
+	}
+
 	@Test
 	void testAddResource() {
 		var mcpSyncServer = McpServer.sync(createMcpTransportProvider())