Currently, the name of the metric is restricted to alphanumeric characters. This restriction was originally put in place to circumvent issues due to systems not supporting certain characters.
However, this restriction does not make a lot of sense since for group names we don't enforce such a restriction.
This also affects the integration of the Kafka metrics, so i suggest removing the restriction.
From now on it will be the responsibility of the reporter to make sure that the metric identifier is supported by the external system.