Support IAM-based authentication on RDS for Postgres

## Tell us about the problem you're trying to solve
Amazon RDS allows accessing Postgres, MySQL, and MariaDB databases using [IAM-based authentication](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/UsingWithRDS.IAMDBAuth.html). A question about this feature was [raised](https://airbytehq-team.slack.com/archives/C021JANJ6TY/p1658532551005969) in the community Slack.

## Describe the solution you’d like
We are currently using Hikari to connect to JDBC sources. [This post ](https://blog.jdriven.com/2021/06/configure-hikari-connection-pool-when-using-rds-iam/)describes a solution for Hiraki to use IAM-based authentication.

## Describe the alternative you’ve considered or used
Current workaround is to generate login/password specifically for Airbyte