Merge pull request #199 from terraform-aws-modules/terraform-provider-githubfile-1584537120162146000

[ci skip] Create "Makefile".

- Update `db_instance` submodule to use same default ca_cert_identifier as the root level module default

* add outputs for the monitoring role arn

* add outputs for the monitoring role arn

* Fixed value in outputs
Co-authored-by: Anton Babenko <anton@antonbabenko.com>

* Add var.performance_insights_retention_period

* Add performance insights retention docs

* add support for max_allocated_storage

* add support for max_allocated_storage

* add support for max_allocated_storage

* max_allocated_storage into documentation

* changed required type to 'number'