Allow Azure AD connection mapping customization

Feature: Allow Azure AD connection mapping customization

Consider providing an administrator of a given MS/Azure connection to be able to set the mapping of MS to Auth0 attributes so that if an email address isn’t set we can use the UPN attribute for example.

If not exposing a mapping to administrators, at least consider doing the fallback from a missing email address to the always-provided UPN

Use-case: Azure AD allows users not to have emails set for their users and in that case the users won’t have an email when created on the Auth0 side. This idea would offer a way to change how the attributes are handled depending what the customer wants to do with them like how you can map in the normal OIDC or SAML connections.