feat: AWS IAM auth for POSTGRES dataSource

[quentin-roche]

Hello,

For my use case, I need Terrakube to connect to RDS. We have a strict no static password, Terrakube already supports S3 access using AWS DefaultCredentialsProvider but does not have a way to do it for dataSources.

This PR allow connecting to RDS Postgres database using the AWS IAM.

Added:

• A custom implementation of PGSimpleDataSource.getConnection that allows pulling and refreshing AWS RDS token
• Two new configs:
  • DatasourceAwsIamAuth (boolean, default: false): Enable pulling Postgres password using AWS IAM
  • DatasourceAwsRegion (string, default: "aws-region-not-set"): The region of the RDS
• A new dependency on: software.amazon.awssdk > rds

Test:

• It was tested on AWS RDS Postgres

Let me know if you want me to change things, this is my first java PR

[alfespa17]

I think it looks good @quentin-roche