fix: Resolve APIKeySecurityScheme parsing failed

Fixes #220

Author: holtskinner

src/a2a/server/apps/jsonrpc/jsonrpc_app.py

@@ -375,7 +375,11 @@ async def _handle_get_agent_card(self, request: Request) -> JSONResponse:
         # The public agent card is a direct serialization of the agent_card
         # provided at initialization.
         return JSONResponse(
-            self.agent_card.model_dump(mode='json', exclude_none=True)
+            self.agent_card.model_dump(
+                mode='json',
+                exclude_none=True,
+                by_alias=True,
+            )
         )
 
     async def _handle_get_authenticated_extended_agent_card(
@@ -392,7 +396,9 @@ async def _handle_get_authenticated_extended_agent_card(
         if self.extended_agent_card:
             return JSONResponse(
                 self.extended_agent_card.model_dump(
-                    mode='json', exclude_none=True
+                    mode='json',
+                    exclude_none=True,
+                    by_alias=True,
                 )
             )
         # If supportsAuthenticatedExtendedCard is true, but no specific