fix: Standardize gRPC extension header to lowercase and update invocation metadata from grpc.aio.ServicerContext to use the correct syntax#676

guglielmo-san wants to merge 6 commits intoa2aproject:maina2aproject/a2a-python:mainfrom

guglielmo-san:guglielmoc/fix_grpc_metadataguglielmo-san/a2a-python:guglielmoc/fix_grpc_metadataCopy head branch name to clipboard