Added CHALLENGE-INVALID, CHALLENGE-TOKEN-INVALID, and VERIFIED-BOT signals
- Added CHALLENGE-INVALID Signal: indicates a request that included a valid bot challenge token.
- Added CHALLENGE-TOKEN-INVALID Signal: indicates a request that did not include a valid bot challenge token.
- Added VERIFIED-BOT Signal: indicates that a bot has been validated to be what it represents itself to be.
Prior change: Updated detection of signals
Following change: Improved detection of signals
