Support AWS IAM authentication

[edgarrmondragon]

• https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/UsingWithRDS.IAMDBAuth.html
• https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/rds/client/generate_db_auth_token.html
• For inspiration: https://github.com/epsylabs/psycopg2-iam