Support for Microsoft Entra ID with Azure PostgreSQL - flexible server

### What problem are you facing?

To be able to access an Azure PostgreSQL via Microsoft Entra ID ( either from an Entra ID User or Managed Identity ), we need to be able to create a user in PostgreSQL which is bound to said identity. See https://learn.microsoft.com/en-us/azure/postgresql/flexible-server/how-to-configure-sign-in-azure-ad-authentication or https://learn.microsoft.com/en-us/azure/postgresql/flexible-server/how-to-connect-with-managed-identity

### How could Crossplane help solve your problem?

Crossplane to create a user in PostgreSQL which is bound to either Entra ID User or Managed Identity according to above documentation