Authenticates an OTel Agent using the client credentials grant type. Supports standard OAuth2 form-encoded requests.
The client_id and client_secret represent the API key and secret generated from the
Unomiq Management API. The API credentials must have the read:traces permission.
The grant_type must be set to client_credentials.
Note: This API should not be called separately for automatic OpenTelemetry instrumentation. Instead, use the OTel OAuth2 Client Credentials Authenticator Extension which handles token retrieval and refresh automatically.