chore(importers): log field names instead of full config on validation failure

The debug log dumped the entire parsed config dict when schema
validation failed. Those blobs can be enormous (inline example data,
multi-line keys) and bury the actual validation error logged just
above. Log the file name and its top-level field names instead.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

superset/commands/importers/v1/utils.py

@@ -230,7 +230,11 @@ def load_configs(
                     prefix,
                     exc.messages,
                 )
-                logger.debug("Config content that failed validation: %s", config)
+                # Log field names only; full values can be huge (e.g. inline
+                # example data) and drown out the validation error above.
+                logger.debug(
+                    "Config fields present in %s: %s", file_name, sorted(config)
+                )
                 exc.messages = {file_name: exc.messages}
                 exceptions.append(exc)