add Azure Active Directory as sql server admin authentication

[mvbugge]

Change

Add the configuration to use AAD as sql server admin authentication.
SQL admin credentials were previously required parameters, this is changed to conditional as they are no longer necessary if AAD is configured to be only authentication method.

Type of Change

• New feature (non-breaking change which adds functionality)

Checklist

• I'm sure there are no other open Pull Requests for the same update/change
• My corresponding pipelines / checks run clean and green without any errors or warnings
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (readme)
• I did format my code

[ghost]

All CLA requirements met.

[AlexanderSehr]

Hey @mvbugge, thanks for the great contribution. Just a few comments and asks.

[AlexanderSehr]

I'll give the template a spin as soon as I can. If the change works in the pipeline, we can merge it

[AlexanderSehr]

Hey @mvbugge , I created a branch with your code to test the changes using pipelines. To make it transparent, I opened a draft PR which is not supposed to be merged.
Anyhow, I added a test file to specifically test the adminitrator variant, but it fails the login. Any idea why this could be these case?

Parameters
"administrators": {
    "value": {
        "azureADOnlyAuthentication": false,
        "login": "U85Z90R82n110u117M7",
        "sid": "<<deploymentSpId>>",
        "principalType": "Application",
        "tenantId": "<<tenantId>>"
    }
}

Error
Status Message: Invalid value given for parameter Login. Specify a valid parameter value. (Code:InvalidParameterValue)

[mvbugge]

@MrMCake I've added the suggestions to the new PR. I suggest trying "azureADOnlyAuthentication": true

[AlexanderSehr]

@mvbugge You nailed it. I successfully tested it in the test PR.