Add aws_instance_tags containing AWS tags attached to the instance

[vmercierfr]

Objective

Add aws_instance_tags containing AWS tags attached to the instance.

Why

We received a feature request to have AWS tags in #37.

Implementation is similar to yet-another-cloudwatch-exporter. To limit cardinality, the tags are published in rds_instance_tags metric.

The metrics looks like:

rds_instance_tags{aws_account_id="<account_id>",aws_region="<aws_region>",dbidentifier="<rds_identifier>",tag_Tag1="value1",tag_Tag2="value2"} 0

So it could be used to join metrics:

max by (aws_account_id, aws_region, dbidentifier) (rds_free_storage_bytes{} * 100 / rds_allocated_storage_bytes{}) + on (aws_account_id, aws_region, dbidentifier) group_left(tag_Environment) rds_instance_tags

How

• Add aws_instance_tags containing AWS tags attached to the instance.

Release plan

• Merge this PR

[vmercierfr]

#sre

[victorboissiere]

LGTM

[dcupif]

LGTM 🚀

[github-actions]

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/rds	80%	➖
github.com/qonto/prometheus-rds-exporter/internal/app/servicequotas	51%	❌
github.com/qonto/prometheus-rds-exporter/internal/app/unit	100%	✔
Summary	82% (535 / 652)	✔

Minimum allowed line rate is 60%