Add support for AWS SSO

[ncw (Nick Craig-Wood)]

@george-matthew

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x18 pc=0x12e0429]

goroutine 66 [running]:
github.com/aws/aws-sdk-go/aws/credentials/stscreds.(*WebIdentityRoleProvider).RetrieveWithContext(0xc000170c60, 0x2179be8, 0xc00003c050, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        github.com/aws/aws-sdk-go@v1.37.3/aws/credentials/stscreds/web_identity_provider.go:111 +0x69

That is a crash from within the s3 SDK which doesn't bode well!

OK Can you give this a go which is the latest stable s3 sdk

v1.56.0-beta.5410.68e2f7432.fix-s3-sso-crash on branch fix-s3-sso-crash (uploaded in 15-30 mins)

If that works - great! If not, I'll investigate further.