[feature]: Allow using private IPs for webhooks

[Exeteres]

Is there an existing issue for this?

• [X] I have searched the existing issues

Summary

Looks like Plane is now prohibiting the creation of webhooks with private IP addresses: https://github.com/makeplane/plane/blob/2c609670c83a82301f41f7a69eca8bac1c8aec37/apiserver/plane/app/serializers/webhook.py#L43-L46

Why should this be worked on?

While blocking private addresses for public installations seems reasonable, it prevents services in environments like VPN or Kubernetes cluster from being used as webhook endpoints. Maybe we should add a configuration option to allow private addresses?

[Exeteres]

I'm sorry, it's a duplicate of #4313 Anyway, it seems like a useful feature that costs nothing to add :D I could submit the PR, if that's okay