As mentioned in OCP bug, adding custom configuration for proxy via manifest is not supported.

Proxy should be added through install-config file only as mentioned in the documentation [1].

[1] https://docs.openshift.com/container-platform/4.16/installing/installing_bare_metal/installing-bare-metal.html#installation-configure-proxy_installing-bare-metal

Adding proxy through custom config via manifests fails to apply on master node.

Bug: https://issues.redhat.com/browse/OCPBUGS-31026

Hence as discussed on the above bug documentation should be updated with the following information like:

"Note: Adding custom proxy configuration via manifests is not supported.
Applying proxy though custom config via manifest fails to get added to master node."

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