Support feature worker declaration from gitlab.teklia.com

Closes #1883 (closed)

• Requires tests

arkindex/process/management/commands/update_system_workers.py

@@ -15,8 +15,12 @@ def parse_config():
     features_parser = parser.add_subparser("features")
     for feature in ArkindexFeature:
         feature_parser = features_parser.add_subparser(feature.value, allow_extra_keys=False, default={})
-        feature_parser.add_option("image", type=str)
+        feature_parser.add_option("image", type=str, default=None)
         feature_parser.add_option("command", type=str, default=None)
+        teklia_worker_parser = feature_parser.add_subparser("teklia_worker", allow_extra_keys=False, default={})
+        teklia_worker_parser.add_option("name", type=str, default=None)
+        teklia_worker_parser.add_option("version", type=str, default=None)
+        teklia_worker_parser.add_option("slug", type=str, default=None)
 
     return parser.parse(settings.BASE_DIR / "system_workers.yml")