add provider delay config for app delete

[talbright]

This is a continuation of #142 to add an additional post_app_delete_delay to address #123.

provider "heroku" {
  "delays"  {
     post_app_delete_delay = 10  
  }
}

[mars]

Very nice. Looks great!

Only the CHANGELOG will need to be updated from master.

[talbright]

I still haven't been able to recreate the issue. Probably I need to create real dynos instead of just the apps per #159 . Might be a good chance to give the fancy new build resource a try.

[talbright]

Looks like I forgot to come back to this! I was never able to reproduce the issue, do you think we should close this or put it in anyways since it was reported in #123? @mars

[talbright]

I'll close this for now, if it comes up again we can raise it back from the 💀

[mars]

I've Terraform destroyed a Space with apps in it sooo many times, never encountered an eventual consistency issue on app delete. I wonder if the initial bug reported was a manifestation of some underlying Private Spaces behavior or bug that has since been changed. ANyway. Thanks for cleaning this up @talbright !