Draft: Migrate cache to use the Arkindex export structure

Refs https://redmine.teklia.com/issues/6576

worker_init_elements/worker.py

@@ -10,6 +10,7 @@ from time import sleep
 
 from arkindex_export import Image as CachedImage
 from arkindex_export import ImageServer as CachedImageServer
+from arkindex_worker.worker.element import ElementMixin
 from arkindex_export import create_database
 
 from arkindex_worker.cache import CachedElement
@@ -58,7 +59,7 @@ class ActivityState(Enum):
     """
 
 
-class InitElementsWorker(BaseWorker):
+class InitElementsWorker(BaseWorker, ElementMixin):
     def configure(self) -> None:
         super().configure()
 
@@ -182,13 +183,9 @@ class InitElementsWorker(BaseWorker):
             "corpus"
         ), "This worker only supports processes on corpora."
 
-        # TODO: Can't use `from arkindex_worker.worker.element.ElementMixin.list_corpus_types`
-        # Because `self.corpus_id` is not set?
-        corpus = self.api_client.request(
-            "RetrieveCorpus", id=self.process_information["corpus"]
-        )
+        self.list_corpus_types()
         type_slugs = {
-            element_type["id"]: element_type["slug"] for element_type in corpus["types"]
+            element_type["id"]: element_type["slug"] for element_type in self.corpus_types.values()
         }
 
         elements = [