Find replacement for secrets.yml as it's deprecated

[murny]

From recent #3346 we are now getting the following deprecation warning:

DEPRECATION WARNING: `Rails.application.secrets` is deprecated in favor of `Rails.application.credentials` and will be removed in Rails 7.2.

We should maybe move to credentials? But this requires a potential organizational shift as Jupiter would hold all the secrets and not Ansible, and we will use a MASTER_KEY to decrypt it.

https://edgeguides.rubyonrails.org/security.html#custom-credentials

[murny]

Perhaps we could just use a simple config_for? https://api.rubyonrails.org/classes/Rails/Application.html#method-i-config_for

This will get around the deprecation but keep everything else the same (could also let us rename secrets to something else too)

[pgwillia]

We won't fix it. Jupiter will be decommissioned in January 2025 after moving to Scholaris, the national repository of DSpace instances hosted by Scholars Portal.