feat: allowed domains for `http.send` in Rego engine

[jiparis]

Currently, http.send domains in Rego engine are locked down for security reasons. We might want to make it configurable. A way would be a server side setting that gets downloaded on attestation init.

• backend
• Docs
• add support for allowlisting custom hostnames during eval command #2335

[migmartri]

Agreed, this could be a instance configuration setting