github.onIssueFieldAdded emits issue events with action "field_added".
automations/watch-github-issue-field-added.automation.ts
account defaults to the project binding. Returns the typed GitHub issue webhook payload with action: "field_added", the required issue_field, the optional new issue_field_value, and the optional previous value under changes.issue_field_value.from. The installation needs Issues read permission and repository access.