Avoid crash when the RDS instance contains tags with unsupported label characters

[vmercierfr]

Objective

Avoid crash when the RDS instance contains tags with unsupported label characters

Why

End-user reported exporter crash when an RDS contains unsupported label characters ( https://github.com/qonto/prometheus-rds-exporter/issues/120).

The ClearPrometheusLabel() was not sanitizing correctly the tag.

Metric names may contain ASCII letters, digits, underscores, and colons. It must match the regex [a-zA-Z:][a-zA-Z0-9:]*. https://prometheus.io/docs/concepts/data_model/

How

• Fixed ClearPrometheusLabel() function to remove unsupported characters from the Prometheus label

Release plan

• [ ] Merge this PR
• [ ] Apply with CI

[github-actions[bot]]

Package	Line Rate	Health
github.com/qonto/prometheus-rds-exporter/internal/app/cloudwatch	88%	✔
github.com/qonto/prometheus-rds-exporter/internal/app/ec2	88%	✔
github.com/qonto/prometheus-rds-exporter/internal/app/exporter	80%	➖
github.com/qonto/prometheus-rds-exporter/internal/app/rds	80%	➖
github.com/qonto/prometheus-rds-exporter/internal/app/servicequotas	51%	❌
github.com/qonto/prometheus-rds-exporter/internal/app/unit	100%	✔
Summary	81% (938 / 1156)	✔

Minimum allowed line rate is 60%