Bugfixes on Metrics

Fixing metrics that was crashing if no labels
Removing unused counters

Flexibility on Prometheus hook

Merge pull request #27 from olxbr/feature/labels-optional-prometheus

Removing labels as mandatory

GDPR protection with message body REDACTED

Now support env var BARTERDUDE_LOG_REDACTED=0 to enable log message body

Connection retry fixed

Merge pull request #20 from olxbr/feature/connection-fail

Add on_connection_fail callback