fix: change database save in DatasourceEditor (#9255)

* fix: change database save in DatasourceEditor

This addresses the issue where pointing a datasource to another database
in the datasource editor is not reflected.

Also addresses:
- a minorcosmetic issue in the datasource editor.
- user/owners list not getting populated

* tests

tests/fixtures/datasource.py

@@ -18,6 +18,7 @@
 datasource_post = {
     "id": None,
     "column_formats": {"ratio": ".2%"},
+    "database": {"id": 1},
     "description": "Adding a DESCRip",
     "default_endpoint": "",
     "filter_select_enabled": True,