Efficient labels

[galargh]

Implement issue labels support efficiently. With integrations/terraform-provider-github@main...galargh:terraform-provider-github:feat/github_issue_labels in place, we can manage all labels for a repository using a single tf resource instead of a resource per label. This greaaaaaaatly reduces the number of GitHub API calls that we'll be doing during plans/syncs/applies.

Testing

• deployed and tested in pl-strflt/github-mgmt

[galargh]

I'm putting this back in draft. The changes in the provider need more work. I'll mark it as ready for review after successful testing in pl-strflt org.

Things to look out for:

• import should import all the labels for the repo to state
• plan/apply (without refresh) should avoid having a side-effect of importing new labels to the state
• refresh should import new labels to the state

[galargh]

And it's ready! You can have a look at all the labels being tracked through https://github.com/pl-strflt/github-mgmt/blob/master/github/pl-strflt.yml

We might want to wait a couple of days to see if integrations/terraform-provider-github#1694 makes it into the next gh provider release since they've been very responsive lately.