Minder's Github Webhook Handler vulnerable to denial of service from un-validated requests

Minder's `HandleGithubWebhook` is susceptible to a denial of service attack from an untrusted HTTP request. The vulnerability exists before the request has been validated, and as such the request is still untrusted at the point of failure. This allows an attacker with the ability to send requests to `HandleGithubWebhook` to crash the Minder controlplane and deny other users from using it. This vulnerability is fixed in 0.0.48.