feat: support client_credentials for service users (#5134)

Request an access_token for service users with OAuth 2.0 Client Credentials Grant. Added functionality to generate and remove a secret on service users.

internal/api/grpc/user/converter.go

@@ -72,6 +72,7 @@ func MachineToPb(view *query.Machine) *user_pb.Machine {
 	return &user_pb.Machine{
 		Name:        view.Name,
 		Description: view.Description,
+		HasSecret:   view.HasSecret,
 	}
 }