auth: allow auth backends prepare_request() to be a coroutine function

Signed-off-by: Florian Scherf <f.scherf@pengutronix.de>

Author: fscherf

aiohttp_json_rpc/rpc.py

@@ -253,7 +253,10 @@ def __call__(self, request):
     async def handle_request(self, request):
         # prepare request
         request.rpc = self
-        self.auth_backend.prepare_request(request)
+        coroutine = self.auth_backend.prepare_request(request)
+
+        if asyncio.iscoroutine(coroutine):
+            await coroutine
 
         # handle request
         if request.method == 'GET':