Add your own _-prefixed requests and notifications to ACP, in both directions, typed and
raw: builder handlers (extRequestHandler, extNotificationHandler), annotations
(@ExtRequest, @ExtNotification) and the senders (sendExtRequest, sendExtNotification).
No API key required.
Full tutorial: https://lab.pollack.ai/docs/acp-java-sdk/tutorial/34-extension-methods
./mvnw package -pl module-34-extension-methods -q
./mvnw exec:java -pl module-34-extension-methods