Add Schedules.get_subscriptions_by_schedule to list a schedule's subscriptions - #1873

Permission denied when trying to create/update comment. This PR is from a fork. GitHub restricts the GITHUB_TOKEN to read-only for fork PRs triggered by the `pull_request` event. To fix this, use the `pull_request_target` event instead: ```yaml on: pull_request_target: types: [opened, synchronize, reopened] permissions: contents: read pull-requests: write ``` Note: `pull_request_target` runs in the context of the base branch. Be cautious when checking out fork code — never run untrusted code from the fork with elevated permissions. For more information, see: https://github.com/MishaKav/pytest-coverage-comment#fork-prs