Update model_usage to an enum

docs/contents/workers/yaml.md

@@ -80,7 +80,16 @@ include:
     : This worker does not support GPUs. It may run on a host that has a GPU, but it will ignore it.
 
 `model_usage`
-: Boolean. Whether or not this worker requires a model version to run. Defaults to `false`.
+: Whether or not this worker requires a model version to run. Defaults to `disabled`. May take one of the following values:
+
+    `required`
+    : This worker requires a model version, and will only be run on processes with a model.
+
+    `supported`
+    : This worker supports a model version, but may run on any processes, including those without model.
+
+    `disabled`
+    : This worker does not support model version. It may run on a process that has a model, but it will ignore it.
 
 `docker`
 : Regroups Docker-related configuration attributes:

tests/conftest.py

@@ -139,7 +139,7 @@ def _mock_worker_run_api(responses):
             "docker_image_name": None,
             "state": "created",
             "gpu_usage": "disabled",
-            "model_usage": False,
+            "model_usage": "disabled",
             "worker": {
                 "id": "deadbeef-1234-5678-1234-worker",
                 "name": "Fake worker",
@@ -206,7 +206,7 @@ def _mock_worker_run_no_revision_api(responses):
             "docker_image_name": None,
             "state": "created",
             "gpu_usage": "disabled",
-            "model_usage": False,
+            "model_usage": "disabled",
             "worker": {
                 "id": "deadbeef-1234-5678-1234-worker",
                 "name": "Fake worker",