Allow customization of Helm components

[mrsimonemms]

• Create Helm functions in that extend the customization functions to Helm-specific format #10966
• Docker Registry #10967
• RabbitMQ*
• Object storage*
• Database*

* These are future pieces of work as unlikely to be required for enterprise customers

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.