✨(backend) add document search indexer

Add indexer that loops across documents in the database, formats them
as json objects and indexes them in the remote "Find" mico-service.

src/backend/impress/settings.py

@@ -99,6 +99,17 @@ class Base(Configuration):
     }
     DEFAULT_AUTO_FIELD = "django.db.models.AutoField"
 
+    # Search
+    SEARCH_INDEXER_BATCH_SIZE = values.IntegerValue(
+        default=100_000, environ_name="SEARCH_INDEXER_BATCH_SIZE", environ_prefix=None
+    )
+    SEARCH_INDEXER_URL = values.Value(
+        default=None, environ_name="SEARCH_INDEXER_URL", environ_prefix=None
+    )
+    SEARCH_INDEXER_SECRET = values.Value(
+        default=None, environ_name="SEARCH_INDEXER_SECRET", environ_prefix=None
+    )
+
     # Static files (CSS, JavaScript, Images)
     STATIC_URL = "/static/"
     STATIC_ROOT = os.path.join(DATA_DIR, "static")