Improve region support

[demeringo]

Problem

At the moment only a limited list of aws_regions is supported.

Solution

We need to match ISO country codes with AWS regions.

Actual region<-> is translation code should be externalized, and even better we should rely on a third party package for this.

Alternatives

Additional context or elements

• Not sure if relevant: https://crates.io/crates/aws-region

[demeringo]

Note: at the moment we suport only the aws eu-based regions.

[demeringo]

Support shoudl be extended to all AWS regions

[demeringo]

Closed by #446