Add option for plugin to automatically create a CloudFront invalidation once deployment is complete

This was discussed briefly in #47. Currently in our “with CloudFront” recipe and in my blog post we recommend invalidating the CloudFront cache after the deployment.

The mechanism suggested for this is to use the shell’s && operator to execute both commands:

gatsby-plugin-s3 deploy --yes && aws cloudfront create-invalidation --distribution-id EXAMPLEDISTRIBUTIONID --paths \"/*\"

This is clunky, it would be nice to have gatsby-plugin-s3 take care of this.

By default I think we should NOT wait for the invalidation to complete, as this may take a long time. We could also add an option to wait for the invalidation to complete.

I suggest these options and defaults:

{
    'cloudfrontDistributionId': undefined,
    'createCloudfrontInvalidation': false,
    'waitForCloudfrontInvalidation': false
}

[jariz]

@JoshuaWalsh The createCloudfrontInvalidation option seems a bit unnecessary to me (or should at least have a true default).
If you’ve configured a CF dist ID, surely you want the plugin to invalidate it? (what other point would there be to setting this)

[joshimbriani]

Sure enough! Thanks for pointing that out, I spent the last 2 days wracking my brain trying to figure out a workaround. I’d still love to implement this feature since presumably if you don’t have to invalidate everything, it’s better for performance.