Security: Implement Webhook JWE (JSON Web Encryption) Encryption Standard

[EDOHWARES]

Description

Provide secure webhook delivery by adding support for JWE payload encryption.

Current Problem

Webhook payloads containing transaction details are transmitted in plain text, exposing data to interception on public networks.

Proposed Solution

Add options to encrypt webhook bodies using the recipient's public key following the JWE (RFC 7516) standard.

Technical Tasks

• Install cryptographic libraries supporting JWE parsing (like `jose`)
• Add public key configuration inputs to the trigger creation form
• Encrypt payload structures in `webhook.service.js` prior to delivery when key exists
• Add developer documentation explaining how to decrypt payloads using private keys

Acceptance Criteria

• Webhooks contain a valid JWE compact serialization payload when encryption is enabled
• Unencrypted deliveries function normally if no public key is configured
• Signature headers are still computed and attached correctly to requests

Testing Requirements

• Encrypt a payload and verify successful decryption using the corresponding private key

Metadata

• Priority: Medium
• Difficulty: High