powerquery SDK - custom connector oauth authentication

[not_the_humans]

I'm attempting to build, for the first time, a custom connector in the power query sdk. Authentication to the api is handled by OAuth 2, with grant-type=client_credentials. If I were to use curl the request would look like this:

curl -u '<Client ID>:<Client Secret>' \
  --data 'grant_type=client_credentials' \
  'https://<domain>/oauth/token'

I can't figure out how, in the SDK, to remove the requirement for the user to authenticate against a URI as they'd be expected to do if the grant-type were authorization_code. StartLogin appears to be a mandatory method when Authentication = OAuth, and within StartLogin a ResourceURI is also mandatory. Any help gratefully received.

[artemus · Accepted solution]

Support for SPN is currently not supported for custom connectors. You could probably implement this yourself using the API key auth type. Another option is to create a service account as a stand in for the service account. The gateway admin portal does support service principal, so maybe that would work for what you are doing?