Implement --s3bucket flag for rain stackset deploy

[Scribbd]

While rain deploy has the flag to use a custom bucket for template and resource upload, this feature is missing for rain stackset.

Inside my organization, we have a bucket set up for organization wide deployments.

I took a dive into the code to look myself. However, Go isn't my forte.

I did identify that inside s3 options are added:

rain/internal/cmd/rain/rain.go

Line 66 in 352763a

func addCommand(label string, profileOptions, bucketOptions bool, c *cobra.Command) {

And that the cmd is added here with this option set on False:

rain/internal/cmd/rain/rain.go

Line 93 in 352763a

addCommand(stackGroup, true, false, stackset.StackSetCmd)

For the life of me, I am unable to find where the flag is interpreted and then used in the rain deploy cmd. I did find the function that checks for the rain-bucket:

rain/internal/aws/s3/s3.go

Lines 171 to 177 in 352763a

	func RainBucket(forceCreation bool) string {
	accountID, err := sts.GetAccountID()
	if err != nil {
	panic(fmt.Errorf("unable to get account ID: %w", err))
	}
	bucketName := BucketName

The functionality would be greatly appreciated.

[Scribbd]

Thank you for your continued effort!

[Scribbd]

As it is now, --s3-bucket is not working correctly. rain stackset has the options. However, the functionality isn't propagated to the subcommands. Thus, rain stackset deploy does not accept the flag. I provided a PR with a fix.