doc: scim definition in the readme

Author: azmeuk

README.md

@@ -2,6 +2,13 @@
 
 An utility command line to help you perform requests against a SCIM server, while validating input and response payloads.
 
+## What's SCIM anyway?
+
+SCIM stands for System for Cross-domain Identity Management, and it is a provisioning protocol.
+Provisioning is the action of managing a set of resources across different services, usually users and groups.
+SCIM is often used between Identity Providers and applications in completion of standards like OAuth2 and OpenID Connect.
+It allows users and groups creations, modifications and deletions to be synchronized between applications.
+
 ## Installation
 
 ```shell
@@ -52,3 +59,8 @@ $ scim2 https://auth.example --header "Authorization: Bearer 12345" query user 2
    }
 }
 ```
+
+scim2-cli belongs in a collection of SCIM tools developed by [Yaal Coop](https://yaal.coop),
+with [scim2-models](https://github.com/yaal-coop/scim2-models),
+[scim2-client](https://github.com/yaal-coop/scim2-client) and
+[scim2-tester](https://github.com/yaal-coop/scim2-tester)