CID-4118: Validate webhook signature

[mohamedlajmileanix]

🛠 Changes made

Validate webhook signature

✨ Type of change

Please delete the options that are not relevant.

• New feature (non-breaking change which adds functionality)

🧪 How Has This Been Tested?

• should process event with valid signature from event json

🏎 Checklist:

• My code follows the style guidelines
• I have performed a self-review of my own code
• My commit message clearly reflects the changes made
• Assigned the appropriate labels (version, PR type, etc.)

[github-actions]

LeanIX GitHub Agent Code Coverage

File	Coverage [98.48%]	🍏
GitHubWebhookService.kt	98.48%	🍏

Total Project Coverage	65.11%	🍏