There are numerous string literals and constants duplicated and spread around different bots. This includes markers (used in PR body and comments) for various bot functionality as well as label names. I would like to collect most of these in a common class in the forge module, something like "PullRequestConstants" next to the existing PullRequestUtils class. By putting just static constants in this class, we can conveniently use "import static" with wildcard to get access to all of them where needed.