Sql auth enhancements

[isaacabraham]

This PR closes #1146

The changes in this PR are as follows:

• Update the API surface to make it easier to interact with.
• Support for mixed-mode authentication.
• Improve type-system by making a dedicated authentication type that caters for sql / entra id / mixed mode.authentication.
• Simply the ARM generation code and remove the unusual "base" code implementation.
• Added some extra unit tests.
• Automatically retrieve the ObjectID of the user if it is not supplied (via an AZ CLI call)

I have read the contributing guidelines and have completed the following:

• Tested my code end-to-end against a live Azure subscription.
• Updated the documentation in the docs folder for the affected changes.
• Written unit tests against the modified code that I have made.
• Updated the release notes with a new entry for this PR.
• Checked the coding standards outlined in the contributions guide and ensured my code adheres to them.

let theServer = sqlServer {
    name "isaac-farmer-entra-test-server"

    // Can still use this if you want to still enable SQL auth, but no longer necessary
    admin_user "super-sql-admin"

    // Use one of the following
    entra_id_admin_user "me@mycompany.com" (ObjectId Guid.Empty) // get via Farmer.Builders.AccessPolicy.findUsers
    entra_id_admin_group "DBA Adminstrators Group"  (ObjectId Guid.Empty) // get via Farmer.Builders.AccessPolicy.findGroups
    entra_id_admin "me@mycompany.com" (ObjectId Guid.Empty) PrincipalType.User
}

[isaacabraham]

@ninjarobot I'm not sure if we've put calls to AZ CLI directly within a builder before - perhaps I should remove that and we simply document "how" to get the object id through Farmer imperatively and let the user decide whether or not to do it?

[ninjarobot]

@ninjarobot I'm not sure if we've put calls to AZ CLI directly within a builder before - perhaps I should remove that and we simply document "how" to get the object id through Farmer imperatively and let the user decide whether or not to do it?

I agree, this would impact users that run Farmer as a library rather than shelling out to the CLI. Library users would likely prefer to do this with the Graph SDK and pass the users or groups to the builder method as an argument.

[isaacabraham]

I'll make that change then.