✨ Implement Post Request Incentives and Refunds

[mariocao]

✨ Feature

Implement an incentive mechanism for posting requests, along with a refund system to ensure fairness and efficiency.

Motivation

This feature incentivizes users to post requests by attaching a reward. It also ensures refunds are provided when requests are not fulfilled or conditions are not met.

Implementation

• Add logic to attach incentives when a request is posted.
• Implement a refund mechanism that returns to the request creator the amount not used (derived from gas used fields)
• Update or extend interfaces as needed.
• Emit relevant events for incentives and refunds.