add support for Gitlab rails secret creation SKIP CHECK CHANGES SKIP UPGRADE

General MR

Please let me know what changes I need to make here! I'm more than willing to work with whomever to bring this MR up to snuff.

Summary

Adds support for the specification of the railsSecret content directly in the BigBang Chart

Reasoning: BigBang allows for the specification of things like the SSO credentials, the redis credentials, and the database credentials. However we cannot specify the contents of the rails Secret directly. Instead, we have to either have the Gitlab chart create the rails secret for us and then back that up, create a kube manifest and then add that to the Bigbang kustomization. This is a messy process and can be very annoying when spinning up blue/green clusters, or even test clusters used to validate things like Gitlab backups (because the rails secrets need to match)

Instead, it would be very handy to be able to specify the contents of the gitlab rails secret directly in the BigBang gitlab addon values. This would allow us to spin up new BigBang clusters that are ready to accept Gitlab-backup restores from another cluster very smoothly. It would also fit inline with how BigBang is handling other Gitlab secrets.

This is a first draft of this MR. If there is anything different you'd like to see please let me know! I am reachable in chat.il4.dso.mil as nicholas.wilburn.1.ctr and would be more than happy to discuss this here or there.