StaticSite: No API definition on `<site URL>/config/basicAuth` endpoint

Static site has supported password protection per: https://docs.microsoft.com/en-us/azure/static-web-apps/password-protection#enable-password-protection. The underlying API used to configure the password is `/config/basicAuth`, and the Azure Portal is using the API version 2021-03-01. However, there is no swagger definition found for this endpoint: https://github.com/Azure/azure-rest-api-specs/blob/9efa37b1a42c4d03eff733d9863dcafbd75d7ee3/specification/web/resource-manager/Microsoft.Web/stable/2021-03-01/StaticSites.json (even not found in the latest api version 2022-03-01).

Start by reading specification/web/resource-manager/Microsoft.Web/stable/2021-03-01/StaticSites.json and compare its existing Static Sites operations with the documented /config/basicAuth endpoint and API version 2021-03-01. Done means the endpoint has a complete API definition consistent with the service and the repository's specification validation passes.

Written by the indexing model from the issue text.