Add velocity forwarding secret file support

[oliverjanka]

Currently the secret can only be specified as string in the config. This makes it almost impossible to run the server within a containerized environment like Kubernetes. Also I don't want secret data to be specified along with 'general' data.

This PR aims to add the functionality to load the secret from an external file (like it is already the default in velocity)

[oliverjanka]

FYI: I only changed the files GlobalConfiguration, VelocityProxy and PaperConfigurations I don't know why rebuildPatches also changed the other patches.

[electronicboy]

Being frank, this has kinda been on the todo list for a while, but if we wanna do this, we would want to maintain consistency with velocities current expected behavior, i.e. the secret if already set should probably be migrated to the file, and we should follow the file naming of velocity so that people can just copy the file over and save confusion

I would maybe await others comments on this, however

[oliverjanka]

@electronicboy I added functionality to migrate in-config secrets to file automatically. I hope this fits what you meant.

[jorishaenseler15]

I really need this feature to run a minecraft server securely on k8s. So i'm looking forward to see the merged pullrequest. @electronicboy

[Nevah5]

Bump

[oliverjanka]

@Machine-Maker what's the status of this issue?