Support OpenStack application credentials

[jobrs]

Support OpenStack application credentials, so that users can easily create restricted technical users to use for authentication of Grafana data sources or Prometheus federation.

Key Results

• OS_APPLICATION_CREDENTIAL_ID, OS_APPLICATION_CREDENTIAL_NAME and OS_APPLICATION_CREDENTIAL_SECRET standard environment variables are supported
• application credentials can be passed via basic authentication (or another mechanism supported both by Prometheus as client and Grafana)

Implementation

Gophercloud already support application credentials since gophercloud/gophercloud#1224. Not tested yet!

[jobrs]

@kayrus fyi

[kayrus]

Gophercloud already support application credentials since gophercloud/gophercloud#1224. Not tested yet!

it is tested in terraform and lyra

In order to handle auth types properly, I created an issue in gophercloud: https://github.com/gophercloud/gophercloud/issues/1566

[jobrs]

implemented, tested and integrated successfully with PR #61, #65, #66