Merge branch 'common_logger' into 'master'

Extensions Logging

See merge request allianceauth/allianceauth!1180

docs/development/custom/index.md

@@ -9,4 +9,5 @@ This section describes how to extend **Alliance Auth** with custom apps and serv
     integrating-services
     menu-hooks
     url-hooks
+    logging
 ```

docs/development/custom/logging.md

@@ -0,0 +1,15 @@
+# Logging from Custom Apps
+Alliance Auth provides a logger for use with custom apps to make everyone's life a little easier.
+
+## Using the Extensions Logger
+AllianceAuth provides a helper function to get the logger for the current module to reduce the amount of
+code you need to write.
+
+```python
+from allianceauth.services.hooks import get_extension_logger
+
+logger = get_extension_logger(__name__)
+```
+
+This works by creating a child logger of the extension logger which propagates all log entries
+to the parent (extensions) logger.