A server side example with a single relation to show values appearing on
the other side

Trivial example of a relation:

juju deploy local:rsetter relation-setter
juju deploy local:rgetter relation-getter

juju add-relation relation-setter relation-getter

This is basically a one way relation, the setter provides some information
and the getter just outputs it when it's finally ready.

The setter is responsible for joining, the getter's hook is null
The setter does nothing on changed or otherwise

It's the getter's responsiblity to use the changed hook and wait,
using a gaurd construct until the secret is not null and then
log that secret.