Accept users, groups, or roles in grants config for dbt-redshift

[dbeatty10]

There might be multiple pages that need updating related to dbt-labs/dbt-redshift#626

Here is at least one:

• https://docs.getdbt.com/reference/resource-configs/grants#database-specific-requirements-and-notes

[matthewshaver]

Pull request this is attached to is still open. Adding blocked by dev label until it is merged.

[mirnawong1]

PR raised by another contributor in this pr: https://github.com/dbt-labs/docs.getdbt.com/pull/5739/files, and below is their suggested content:

By default granting to / revoking from is only applicable for Redshift users (not groups or roles).

To configure grants for roles or groups, they need to be clearly demarcated as such with a prefix:

• To grant access on a model to role_analyst, you need to specify them as ROLE role_analyst.
• To grant access on a model to group_finance, you need to specify them as GROUP group_finance.

General example:

{{ config(grants = {'select': ['ROLE role_analyst']}) }}

Redshift requires the USAGE permission to be granted on schemas for object permissions to be effective. Please refer to AWS's documentation for more context:

• AWS Redshift SQL Reference - GRANT command

In order to grant USAGE, use post-hooks.