[Other]: Analysts' Guide - Databricks token documentation

### Description

When generating a new access token, the users are now prompted to select the API scope(s). It'd be good if guidance on this is added to the AG.

### Why this is important?

For `write_df_to_delta()`, the following scopes are needed: `files`, `sql` and `unity-catalog`, otherwise the function errors out. For simplicity, my unit has been selecting `all-apis` when generating a new access token.

Start with the Analysts' Guide section covering Databricks access-token generation and the guidance around write_df_to_delta(). Document that files, sql, and unity-catalog scopes are required, and mention the all-apis option; done when users can select the needed scopes and avoid the reported error.

Written by the indexing model from the issue text.