fix sample

Author: guglielmo-san

samples/hello_world_agent.py

@@ -11,7 +11,7 @@
 from a2a.compat.v0_3.grpc_handler import CompatGrpcHandler
 from a2a.server.agent_execution.agent_executor import AgentExecutor
 from a2a.server.agent_execution.context import RequestContext
-from a2a.server.apps import A2AFastAPIApplication, A2ARESTFastAPIApplication
+from a2a.server.routes import AgentCardRoutes, JsonRpcRoutes, RestRoutes
 from a2a.server.events.event_queue import EventQueue
 from a2a.server.request_handlers import GrpcHandler
 from a2a.server.request_handlers.default_request_handler import (
@@ -190,22 +190,29 @@ async def serve(
         agent_executor=SampleAgentExecutor(), task_store=task_store
     )
 
-    rest_app_builder = A2ARESTFastAPIApplication(
+    agent_card_routes = AgentCardRoutes(
         agent_card=agent_card,
-        http_handler=request_handler,
+        card_url='/.well-known/agent-card.json',
+    )
+    # JSON-RPC
+    jsonrpc_routes = JsonRpcRoutes(
+        agent_card=agent_card,
+        request_handler=request_handler,
+        rpc_url='/a2a/jsonrpc/',
         enable_v0_3_compat=True,
     )
-    rest_app = rest_app_builder.build()
-
-    jsonrpc_app_builder = A2AFastAPIApplication(
+    # REST
+    rest_routes = RestRoutes(
         agent_card=agent_card,
-        http_handler=request_handler,
+        request_handler=request_handler,
+        rpc_url='/a2a/rest',
         enable_v0_3_compat=True,
     )
 
     app = FastAPI()
-    jsonrpc_app_builder.add_routes_to_app(app, rpc_url='/a2a/jsonrpc/')
-    app.mount('/a2a/rest', rest_app)
+    app.routes.extend(agent_card_routes.routes)
+    app.routes.extend(jsonrpc_routes.routes)
+    app.routes.extend(rest_routes.routes)
 
     grpc_server = grpc.aio.server()
     grpc_server.add_insecure_port(f'{host}:{grpc_port}')