Webhooks helps you to trigger some actions on your server when an event
happens with you repositories.
Key: a string used to "sign" the requests to your server. You can create it
using any character you want: letters, digits and any symbol.
The server will create a HMAC over the payload using SHA512 and will add
HTTP header X-RocketGit-Signature: <signature>. It is
recommended to verify it before parsing the body, for security reasons.
It is not generated for application/x-www-form-urlencoded type.