Add feature to blacklist IPs/domains

[pihme]

In order to run http worker in Camunda Cloud SaaS we need a feature to blacklist certain IPs / domains from being accessed.

Otherwise an attacker could use the running http worker to access/modify information within our cluster. Same will hold true for self-managed deployments.

This may become obsolete for Camunda Cloud SaaS if the network topology changes and each resource only sees the other resources it is supposed to see.