Flutter tutorial for "Connect to external Amazon DynamoDB data sources" ends with inaccurate code snippet

**Describe the content issue**:
Step 5 here[1] points to a "generated Data client" but no examples of creating this client are found within the Flutter documentation. Further, it looks like the example code snippet is actually from the "React" documentation.

Diving deeper into the documentation, I see that to invoking a custom query within flutter is a bit more complicated[2].

1. Can we have the docs updated with a working example?
2. Is there any supporting documentation for the "Amplify.API.query()" method/creating valid requests?

**URL page where content issue is**:
[1] https://docs.amplify.aws/flutter/build-a-backend/data/connect-to-existing-data-sources/connect-external-ddb-table/#step-5---invoke-custom-queries-or-mutations

[2]https://docs.amplify.aws/flutter/build-a-backend/data/custom-business-logic/#step-3---invoke-the-custom-query-or-mutation

Start with the Flutter page's “Step 5 — Invoke custom queries or mutations” section and compare its snippet with the linked custom business logic page and the React documentation. Update the Flutter guidance with a working generated Data client example and explain valid Amplify.API.query() requests, then verify both linked documentation paths are consistent.

Written by the indexing model from the issue text.