fill the readme

README.md

 # keycloak-scim-client
 
+This extension add [SCIM2](http://www.simplecloud.info) client capabilities to Keycloak. (See [RFC7643](https://datatracker.ietf.org/doc/html/rfc7643) and [RFC7644](https://datatracker.ietf.org/doc/html/rfc7644)).
+
+## Overview
+
+### Motivation
+
+We want to build a unified collaborative platform based on multiple applications. To do that, we need a way to propagate immediately changes made in Keycloak to all these applications. And we want to keep using OIDC or SAML as the authentication protocol.
+
+This will allow users to collaborate seamlessly across the platform without requiring every user to have connected once to each application. This will also ease GDRP compliance because deleting a user in Keycloak will delete the user from every app.
+
+### Technical choices
+
+The SCIM protocol is standard, comprehensible and easy to implement. It's a perfect fit for our goal.
+
+We chose to build application extensions/plugins because it's easier to deploy and thus will benefit to a larger portion of the FOSS community.
+
+#### Keycloak specific
+
+This extension uses 3 concepts in KC :
+- Event Listener : it's used to listens for changes and transform them in SCIM calls.
+- Federation Provider : it's used to set up all the SCIM service providers without creating our own UI.
+- JPA Entity Provider : it's used to save the mapping between the local IDs and the service providers IDs.
+
+Because the event listener is the source of the SCIM flow, and it is not cancelable, we can't have strictly consistent behavior in case of SCIM service provider failure. 
+
+## Usage
+
+### Installation
+
+> For now, it's doesn't't work on Quarkus which is the default after version 16.x.x. 
+
+1. Download the [latest version](https://lab.libreho.st/libre.sh/scim/keycloak-scim/-/jobs/artifacts/main/raw/target/keycloak-scim-1.0-SNAPSHOT-jar-with-dependencies.jar?job=package)
+2. Put it in `/opt/jboss/keycloak/standalone/deployments/`.
+
+### Setup
+
+#### Add the event listerner
+
+1. Go to `Admin Console > Events > Config`.
+2. Add `scim` in `Event Listeners`.
+3. Save.
+
+![Event listener page](/docs/img/event-listener-page.png)
+
+#### Create a federation provider
+
+1. Go to `Admin Console > User Federation`.
+2. Click on `Add provider`.
+3. Select `scim`.
+4. Configure the provider ([see](#configuration)).
+5. Save.
+
+![Federation provider page](/docs/img/federation-provider-page.png)
+
+### Configuration
+
+TODO
+
+### Sync
+
+TODO
+
+
+**[License AGPL](/LICENSE)**