add details about the provisioning options in the README

Signed-off-by: Julien Veyssier <[email protected]>

README.md

@@ -190,6 +190,41 @@ is enabled.
 ],
 ```
 
+### 4 Provisioning scenarios
+
+* Create users if they don't exist
+    * Accept connection of existing users (from other backends) and update their attributes:
+      ``` php
+      'user_oidc' => [
+          'auto_provision' => true, // default: true
+          'soft_auto_provision' => true, // default: true
+      ],
+      ```
+    * Do not accept connection of users existing in other backends:
+	  ``` php
+	  'user_oidc' => [
+		  'auto_provision' => true, // default: true
+		  'soft_auto_provision' => false, // default: true
+	  ],
+	  ```
+* Do not create users if they don't exist
+    * Update attributes of existing users (create by user_oidc or any other backend):
+	  ``` php
+	  'user_oidc' => [
+	  	'auto_provision' => true, // default: true
+	  	'soft_auto_provision' => true, // default: true
+	  	'disable_account_creation' => true, // default: false
+	  ],
+	  ```
+    * Do not update attributes of existing users:
+      ``` php
+      'user_oidc' => [
+          'auto_provision' => false, // default: true
+      ],
+      ```
+
+
+
 ### UserInfo request for Bearer token validation
 
 The OIDC tokens used to make API call to Nextcloud might have been generated by an external entity.