Integrate Rails 5.2 secrets

[ortegacmanuel]

by using rails 5.2 there is a new way to handle secrets (master key and such).

Can you put that in inline_forms? Maybe we don't even need Figaro any more! Yay!

https://medium.com/@wintermeyer/goodbye-secrets-welcome-credentials-f4709d9f4698

[ortegacmanuel]

@acesuares If you have extra comments about this, just add them here.