[AwsVpcPeering] region validation

[vandjelk]

Description

Currently if user apply invalid AwsVpcPeering.spec.remoteRegion following error will appear in status condition

operation error EC2: DescribeVpcs, get identity: get credentials: failed
to refresh cached credentials, operation error STS: AssumeRole, https
response error StatusCode: 0, RequestID: , request send failed, Post
"https://sts.fake-region.amazonaws.com/": dial tcp: lookup
sts.fake-region.amazonaws.com: no such host

If possible we should introduce some AWS region validation on SKR side, otherwise KCP validation is fine as well.

[ngrkajac]

@vandjelk Could we have SKR validation without the Cloud Manager SKR active component?

[vandjelk]

If we identify all regions, we can add XValidationRule on AwsVpcPeering API.

Something like this for example https://gist.github.com/rams3sh/4858d5150acba5383dd697fda54dda2c

Most of the regions occur in combination of 2 letter followed by "-" followed by a combination of direction based word , followed by a "-" and then a digit.
Ref : AWS' regions are listed here https://aws.amazon.com/about-aws/global-infrastructure/regions_az
General Regex - (af|ap|ca|eu|me|sa|us)-(central|north|(north(?:east|west))|south|south(?:east|west)|east|west)-\d+
Note: Availability Zone - Since AZ has a letter added to a region, it can be of following regex:-
(af|ap|ca|eu|me|sa|us)-(central|north|(north(?:east|west))|south|south(?:east|west)|east|west)-\d+[a-z]{1}

We should anyway validate the regex against the region list provided in Regions and Zones - Amazon Elastic Compute Cloud