docs: add SCIM overview to README

docs/admin/scim/README.md

@@ -1,12 +1,15 @@
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 tags:
-  - administration
-  - scim
+- administration
+- scim
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 # Overview
 
-Please use the left navigation menu to browse the content of this section while we are still working on developing content for `Overview` page.
+**S**ystem for **C**ross-domain **I**dentity **M**anagement, in short **SCIM**, is a specification that simplifies the exchange of user identity information across different domains. The Janssen Server provides implementation for the SCIM specification.
 
-!!! Contribute
-    If you’d like to contribute to this document, get started with the [Contribution Guide](https://docs.jans.io/head/CONTRIBUTING/#contributing-to-the-documentation)
+The specification defines reference schemas for users and groups along with REST API to manage them. For more details, refer to the current version of the specification that is governed by the following documents: [RFC 7642](https://tools.ietf.org/html/rfc7642), [RFC 7643](https://tools.ietf.org/html/rfc7643), and [RFC 7644](https://tools.ietf.org/html/rfc7644).
+
+Developers can think of **SCIM** merely as a **REST API** with endpoints exposing **CRUD** functionality (create, read, update and delete).
+
+This section covers how to configure, protect and monitor the Janssen Server SCIM module and its APIs.