Add an `is_certified` key to indicate certified datasets on the `/api/v1/dashboard/{{id}}/datasets` API

What is the problem or goal the end user is trying to solve or accomplish?

Users would like to quickly identify which datasets used in a dashboard are certified through the API.

How are they solving it currently?

Right now they need to:

1. Get all dataset IDs using the /api/v1/dashboard/{{id}}/datasets endpoint.

2. For each dataset ID, use the /api/v1/dataset/{{id}} to check if it has any certification info in the extra field.

What is the recommended solution by the Customer?

Create a new key (for example is_certified) to the dataset payload/schema and expose this key in the /api/v1/dashboard/{{id}}/datasets endpoint.