Allow for custom timeout in watch request

this will allow to set a custom aiohttp.ClientTimeout object
when making the ?watch=true request to Kubernetes API if needed.

related issue 204

kopf/clients/watching.py

@@ -201,7 +201,7 @@ async def watch_objs(
     # Talk to the API and initiate a streaming response.
     response = await context.session.get(
         url=resource.get_url(server=context.server, namespace=namespace, params=params),
-        timeout=aiohttp.ClientTimeout(total=None),
+        timeout=config.WatchersConfig.session_timeout,
     )
     response.raise_for_status()
 

kopf/config.py

@@ -3,6 +3,8 @@
 import logging
 from typing import Optional
 
+import aiohttp
+
 from kopf.engines import logging as logging_engine
 
 format = '[%(asctime)s] %(name)-20.20s [%(levelname)-8.8s] %(message)s'
@@ -121,3 +123,6 @@ class WatchersConfig:
 
     watcher_retry_delay: float = 0.1
     """ How long should a pause be between watch requests (to prevent flooding). """
+
+    session_timeout: aiohttp.ClientTimeout = aiohttp.ClientTimeout(total=None)
+    """ aiohttp ClientTimeout object to use in watch request. """