As a pulp-operator user, I can add arbitrary settings to settings.py
The Docker plugin is adding a new setting, which cannot be set without a change to pulp-operator.
When travis used ansible-pulp to install, arbitrary settings could be added with an ansible variable `pulp_settings`.
All values in pulp_settings (after being merged with the default settings) are added to settings.py in the jinja template.
Something similar could be added to the operator https://github.com/pulp/pulp-operator/blob/fd6b7d92f057d369cd11489aa6e02cdc5a0000f4/roles/pulp-api/templates/pulp-server.config-map.yaml#L28-L30