Counter name in 'identity.authenticate.' metric doesn't render correctly

~~~
Payload={'message_id': 'be5ccc6e-2eb8-4423-8a23-d90d202c44b3', 'publisher_id': 'telemetry.publisher.jt-ecosys-ctrl02-l4-r3-u23.cloud.internal', 'event_type': 'metering', 'priority': 'SAMPLE', 'payload': [{'source': 'openstack', 'counter_name': "$.payload.outcome - $.payload.outcome + 'identity.authenticate.' + $.payload.outcome",'action': 'authenticate', 'outcome': 'failure'}
~~~

'counter_name' in above metric should've been rendered as 'identity.authenticate.failure' or 'identity.authenticate.success' depending upon the 'outcome' field in the payload.

Scrapping tools like Prometheus fail to scrape these metrics due to invalid metric names.
~~~
2023-06-19 08:34:34 [ERROR] prometheus failed scrapping metric [plugin: Prometheus, error: "ceilometer_$_payload_outcome - $_payload_outcome + 'identity_authenticate_' + $_payload_outcome" is not a valid metric name]
2023-06-19 08:34:34 [ERROR] prometheus failed scrapping metric [plugin: Prometheus, error: "ceilometer_$_payload_outcome - $_payload_outcome + 'identity_authenticate_' + $_payload_outcome" is not a valid metric name]
2023-06-19 08:34:34 [ERROR] prometheus failed scrapping metric [plugin: Prometheus, error: "ceilometer_$_payload_outcome - $_payload_outcome + 'identity_authenticate_' + $_payload_outcome" is not a valid metric name]
~~~