Authenticate to New SecOps/Chronicle API via PowerAutomate

I’m trying to authenticate to the new Chronicle API using PowerAutomate. It’s been working using the old API, but I’m not sure how to set it up for the new API. Has anyone done it or have any advice? 

The issue is the authentication methods I see all involve client libraries or the CLI, but in PowerAutomate there is not a pre-built integration that I see, so I’m just using HTTP requests. 

Previous Method

URL: https://REMOVED.siemplify-soar.com/api/external/v1/cases/CreateManualCase

Authentication Method: AppKey

New Method

URL: https://us-chronicle.googleapis.com/v1alpha/projects/REMOVED/locations/us/instances/REMOVED/legacyCases:createManualCase

Authentication Method: ?

I’ve tried API keys (https://docs.cloud.google.com/docs/authentication/api-keys-use#rest) but got an error: 

• Action 'Using_API_Keys' failed: API keys are not supported by this API. Expected OAuth2 access token or other authentication credentials that assert a principal. See https://cloud.google.com/docs/authentication

If you have not used PowerAutomate, it is sort of like the SOAR Playbook functionality, but you can't write your own actions using Python. I'm essentially using HTTP API request actions, though I can string several together and do data operations if needed.