Narrow scope of candidate issues using tags

[danielrbradley]

When opening a pull request for a provider upgrade we need to find all issues it might close.

Previously, we filtered by author, but issues might be opened by different users to the PR if the tool is run locally.

We also add the hidden piece of text pulumiupgradeproviderissue within the body for searching. However, this takes a few seconds to be indexed after the issues is created resulting in issues not being linked to the PR.

Currently, we fetch the 100 latest open issues and check the titles client-side. If there's been more than 100 issues since an upgrade issue was opened, then it won't be included and auto-closed with the PR.

As an alternatively approach, we could allow a label to be specified to be added to all issues which we can also use for filtering the initial search. Our expectation is that label-based search should be immediately indexed and not delayed like the issue text and should therefore be more reliable.

See also:

• Stop filtering on search token when finding applicable issues #293
• upgrade-provider no longer adds Fixes keyword and issue to automatic PRs #291