Feat auth: allow additional secrets as env variables

[Mikey032]

What kind of change does this PR introduce?

Feature

What is the current behavior?

It is currently not possible to pass values of other secrets to the auth service. This means adding external identity providers will cause you to add the secrets in plain text.

What is the new behavior?

By using envFrom we can reference a secret that contains all the env variables to configure for example an external identity provider.

Additional context

None