[Bug] Service Principal add or remove password credential fails

Currently a service principal update that either adds or removes a password credential fail, complaining about an additionalProperties field.

In addition, the api call that these calls are making appears to be incorrect, making a PATCH request. When adding or removing a password the graph api appears to require a POST call to a differing endpoint (the graph api docs note that the PATCH request is no longer valid for add or remove).

This was validated by using the graph api sdk directly, which was able to make the add/remove request directly.

While in the graph sdk it appears that