feat: add option to disable oversized payload check in A2AFastAPIApplication

Author: sokoliva

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

@@ -77,6 +77,7 @@ def __init__(  # noqa: PLR0913
             [AgentCard, ServerCallContext], AgentCard
         ]
         | None = None,
+        disable_content_length_check: bool = False,
     ) -> None:
         """Initializes the A2AFastAPIApplication.
 
@@ -94,6 +95,8 @@ def __init__(  # noqa: PLR0913
             extended_card_modifier: An optional callback to dynamically modify
               the extended agent card before it is served. It receives the
               call context.
+            disable_content_length_check: An optional, if True disables the check
+              for oversized payloads.
         """
         if not _package_fastapi_installed:
             raise ImportError(
@@ -108,6 +111,7 @@ def __init__(  # noqa: PLR0913
             context_builder=context_builder,
             card_modifier=card_modifier,
             extended_card_modifier=extended_card_modifier,
+            disable_content_length_check=disable_content_length_check,
         )
 
     def add_routes_to_app(