feat: add optional lastModified field to Annotations record with backward compatibility (#568)

Resolves #565

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

Author: tzolov

mcp-core/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

@@ -653,7 +653,13 @@ public interface Annotated {
 	@JsonIgnoreProperties(ignoreUnknown = true)
 	public record Annotations( // @formatter:off
 		@JsonProperty("audience") List<Role> audience,
-		@JsonProperty("priority") Double priority) { // @formatter:on
+		@JsonProperty("priority") Double priority,
+		@JsonProperty("lastModified") String lastModified
+		) { // @formatter:on
+
+		public Annotations(List<Role> audience, Double priority) {
+			this(audience, priority, null);
+		}
 	}
 
 	/**