Function get_protocols_handler 

async fn get_protocols_handler(
    __arg0: AuthenticatedClientRequest<Request>,
) -> Result<ArminiusResponse<Response>, ThirdPartyError>

Handler for GET /_matrix/client/v3/thirdparty/protocols (See https://spec.matrix.org/v1.15/client-server-api/#get_matrixclientv3thirdpartyprotocols).

Fetches the overall metadata about protocols supported by the homeserver.

NOTE: For now, there are no supported third-parties, so this always returns an empty map.