Support AWS S3 migration source via aws-sdk-go-v2

[meatballhat]

Is your feature request related to a problem? Please describe.

At $job I'm required to use AWS via SSO, which means that credentials are cached locally in a way that's not directly compatible with aws-sdk-go (v1). Getting the aws_s3 migration source to work requires additional manual steps, so it's possible, but an annoyance. More seriously, the aws-sdk-go-v2 library seems to be where most effort is being made these days (anecdotal, I admit).

Describe the solution you'd like

Support a migration source that uses the aws-sdk-go-v2 library which already (at current version) supports SSO auth. I have such a migration provider implemented already in a private repository, so I'm mostly opening this issue to see if adding such a provider would be accepted, and if so, should it replace aws_s3 or be available as an alternative (aws_s3_v2?).

Describe alternatives you've considered

Using the current aws_s3 migration source is possible when manually adding the necessary environment variables, which are only available via a web tool and can't be scripted AFAICT.

[meatballhat]

FYI here is an extracted version of the migration source provider for consideration: https://github.com/rstudio/golang-migrate-source-aws-s3-v2

[iwarapter]

Hey the sdk v1 is also approaching EOL now.