• What is the nature and description of the request?

Implement the same feature from awx-operator, to mount galaxy-operator 

https://github.com/ansible/awx-operator/blob/devel/docs/user-guide/advanced-configuration/custom-volume-and-volume-mount-options.md

• Why does the customer need this? 

Customer need to customize some files like `/etc/hosts`, ansible.cfg, ...