Foreman behind proxy and firewall

Problem:
Foreman is behind proxy and firewall. Internet access is only possible through this proxy. I could not find any information on such a setup. How do I have to setup foreman fetching files from the Internet using this proxy?

Expected outcome:
Some Information to find on how to set up Foreman to access proxies to access the internet to fetch files.

Foreman and Proxy versions:

foreman-2.0.0-1.el7.noarch
foreman-cli-2.0.0-1.el7.noarch
foreman-debug-2.0.0-1.el7.noarch
foreman-dynflow-sidekiq-2.0.0-1.el7.noarch
foreman-installer-2.0.0-1.el7.noarch
foreman-postgresql-2.0.0-1.el7.noarch
foreman-proxy-2.0.0-1.el7.noarch
foreman-release-2.0.0-1.el7.noarch
foreman-release-scl-7-2.el7.noarch
foreman-selinux-2.0.0-1.el7.noarch
rubygem-foreman_maintain-0.6.2-1.el7.noarch
tfm-rubygem-hammer_cli_foreman-2.0.2-1.el7.noarch

Foreman and Proxy plugin versions:

Distribution and version:

CentOS Linux release 7.7.1908 (Core)
Derived from Red Hat Enterprise Linux 7.7 (Source)

Other relevant data:

It doesn’t take much. Read section 5.9 HTTP(S) Proxy in the current manual. If you sync repos other than CentOS, some may redirect from the initial URL and require whitelisting those URLs, too. If you are using Squid, review your logs and grep for rejects.

We operate in a very strict environment and have no problem accessing what we need.