[Custom App Webhooks] Webhook events: share, reward

Problem: Previously, our webhook and API payloads were rigid, causing challenges in adapting to various integration requirements. The existing system was cumbersome for the PS team, requiring multiple API calls and elongated timelines for updates.

Solution: 

• Event Inclusion: We have incorporated all events currently missing from our Custom App Webhooks, including share and reward events.
• Liquid Payloads: Employing Liquid payloads enables more dynamic data structure and flexibility. This approach offers a quicker and simpler alternative to updating webhook or API payloads, sidestepping many backward compatibility issues.
• Default Payloads: Default Liquid payloads have been established for each new event, which can easily be customized per your requirements.