rad should validate that the AWS region specified (in the flag or interactive) is a valid region

[asilverman]

Overview of feature request

Since rad doesn't do this at the moment, if the user makes a mistake they will need to reinstall the radius control plane which is not a great user experience. Preferably instead of statically whitelisting the values we should fetch them from AWS API (as new regions can and will be added over time)

Use the equivalent REST API to get the following (reference https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeRegions.html)

aws ec2 describe-regions --all-regions --output json | jq ".Regions[].RegionName"
"af-south-1"
"eu-north-1"
"ap-south-1"
"eu-west-3"
"eu-west-2"
"eu-south-1"
"eu-west-1"
"ap-northeast-3"
"ap-northeast-2"
"me-south-1"
"ap-northeast-1"
"me-central-1"
"sa-east-1"
"ca-central-1"
"ap-east-1"
"ap-southeast-1"
"ap-southeast-2"
"ap-southeast-3"
"eu-central-1"
"us-east-1"
"us-east-2"
"us-west-1"
"us-west-2"

Definition of done:

• Investigate how do we get the supported regions in AWS #3922
• https://github.com/project-radius/radius/issues/5155
• For flags we should validate that the value provided belongs to the set
• Add unit tests

AB#10389

[Reshrahim]

Need to explore if the region is a needed configuration for an AWS provider in rad cli. Can this part of the bicep?. Exploration tracked in #6376

[willtsai]

Let's fix this issue in the CLI first for public-release and follow with the Bicep flavor of the implementation.

[Reshrahim]

This is fixed by listing the available AWS regions and prompting the user to pick one from the list.