new: [smtp-extern] new charm #33

Est-ce qu’il y a besoin d’étoffer ?
ou bien le charm est assez clair et simple comme ça ?

Je me demande s’il y a une raison pour que le charm s’appelle smtp-extern mais que le service s’appelle smtp-server (ou bien est-ce que c’est le nom de la relation smtp-server )?

J’ai eu l’impression en explicant à Stéphan que ça apportait de la confusion.

Ne faudrait-il pas tout renommer en "smtp-server-config" ou "smtp-extern-config" pour plus de clarté ?

There are 3 notions:

service

You run or set up services. Your compose.yml defines services. When they are
up, they will provide functionalities. They often run in individual containers.
charm

A service is managed by a charm, that explains how to set it up. The charm is like
a recipee. You can have several services using the same rules to be managed, they
would then all use the same charm.
relation

services are connected by relations. The relation describe the type of connection
it want to establish with another service.

Your PR is providing us a new charm. It can't provide a service ! It doesn't make sense: services are what the charm are building and managing on each host that will use compose.

So your charm is called smtp-extern. It could be called smtp-stub, as it'll act as a real smtp service (implemented by a smtp charm, that doesn't exist yet !), but your charm smtp-stub doesn't really implement anything : it stands for a service that is managed externally from compose.

It manages to stand for a full server because it provides the same interface: it implements the relation smtp-server (which a full hypothetical smtp charm would do also).

So any other charm requiring to connect to a smtp server only has to ask for a service satisfying the relation smtp-server. Many different charms could actually implement that. The smtp-stub charm allows you to plug in values directly and allow the script smtp_server-relation-joined on the other end to implement its own intelligence to use the smtp-server values.

I have made some minor changes, a few tests, and pushed your charm !
Many thanks !