adjust registered by to managed by on db aslo remove url and api key on adding sites for gm

backend/apps/sync/serializers.py

@@ -7,8 +7,8 @@ class ActiveSiteSerializer(serializers.ModelSerializer):
     id = serializers.IntegerField(source="pk", read_only=True)
     # Never echo the outbound site API key back to the browser by default.
     has_api_key = serializers.SerializerMethodField()
-    registered_by_name = serializers.CharField(
-        source="registered_by.display_name", read_only=True, allow_null=True
+    managed_by_name = serializers.CharField(
+        source="managed_by.display_name", read_only=True, allow_null=True
     )
 
     class Meta:
@@ -19,8 +19,8 @@ class ActiveSiteSerializer(serializers.ModelSerializer):
             "name",
             "api_base_url",
             "has_api_key",
-            "registered_by",
-            "registered_by_name",
+            "managed_by",
+            "managed_by_name",
             "is_active",
             "last_synced_at",
             "last_sync_status",
@@ -31,8 +31,8 @@ class ActiveSiteSerializer(serializers.ModelSerializer):
         read_only_fields = [
             "id",
             "has_api_key",
-            "registered_by",
-            "registered_by_name",
+            "managed_by",
+            "managed_by_name",
             "last_synced_at",
             "last_sync_status",
             "last_sync_message",