📝(docs) light doc about org & SP

This introduces a very light documentation about
the newly introduced models.

docs/serviceProviders.md

@@ -0,0 +1,28 @@
+# ServiceProvider model
+
+## Purpose
+
+The `ServiceProvider` model represents a ... service provider, also known as "tools using some data from this project".
+
+
+## Link with the `Organization` model
+
+An organization can be linked to several service providers. 
+The goal here, is to allow users of an organization to have access, to a service provider or not.
+The first implementation does not have any feature related, but the first feature will probably be
+to list applications visible in the "all application menu" (aka "la gaufre").
+
+
+## Link with the `Team` model
+
+A team can be linked to several service providers.
+This is used as a filter when a service provider calls the resource server, only the teams linked to
+this service provider are returned. This is mandatory for data segregation: we don't want all service
+providers to be able to list all data regarding other service providers.
+
+
+## Limitations
+
+There is currently no way to provision all the service providers automatically. So when a service provider
+creates a team via the resource server, we create the `ServiceProvider` on the fly, without any understandable name.
+This will need to be improved later.