Merge pull request #16 from taskbadger/sk/external-id

Document Task external_id field

Author: snopoke

docs/data_model.md

@@ -71,6 +71,13 @@ The main attributes or a task are:
 :   The name of the queue the task was submitted to. This is set automatically by the Celery and
     Procrastinate integrations and can also be set explicitly when creating or updating a task.
 
+<a name="external_id"></a>
+`external_id`
+
+:   An identifier from the originating system (e.g. a Celery task ID) that lets you correlate a task
+    with its logs. Set it when creating or updating a task, then filter tasks by exact match on this
+    value in the web UI.
+
 ### Example Task
 
 ```json
@@ -97,7 +104,8 @@ The main attributes or a task are:
   "tags": [
     {"environment": "production"}
   ],
-  "queue": "default"
+  "queue": "default",
+  "external_id": "celery-abc-123"
 }
 ```
 

docs/python-celery.md

@@ -218,7 +218,7 @@ Task Badger will create task records for each inner invocation with metadata sim
 }
 ```
 
-**Opting out**
+## Opting out
 
 If you want to prevent TaskBadger from tracking a particular execution, set the `taskbadger_track` header (False) when publishing: