v2.3.1

• Improved logging on callback errors within Revalee.Service.
• Added ongoing heartbeat to activate recurring tasks.
• Added HTTP response status codes from recurring tasks.
• Added public event that handles activation failures for recurring tasks.
• Removed all HTTP Expect 100 Continue behavior.
• Fix: Allow explicit default port numbers on callback URLs.
• Fix: Revalee.Service now stores DateTime.MinValue callback times properly.
• Fix: Task deletion behavior is corrected within the scheduling hashtable.