chore: Migrate json field names to camelCase (3/n)

PiperOrigin-RevId: 758394880

src/google/adk/cli/fast_api.py

@@ -150,7 +150,7 @@ class InMemoryExporter(export.SpanExporter):
     self._spans.clear()
 
 
-class AgentRunRequest(BaseModel):
+class AgentRunRequest(common.BaseModel):
   app_name: str
   user_id: str
   session_id: str
@@ -179,6 +179,10 @@ class RunEvalResult(common.BaseModel):
   session_id: str
 
 
+class GetEventGraphResult(common.BaseModel):
+  dot_src: str
+
+
 def get_fast_api_app(
     *,
     agent_dir: str,
@@ -804,7 +808,7 @@ def get_fast_api_app(
           root_agent, [(from_name, to_name)]
       )
     if dot_graph and isinstance(dot_graph, graphviz.Digraph):
-      return {"dot_src": dot_graph.source}
+      return GetEventGraphResult(dot_src=dot_graph.source)
     else:
       return {}