KEYCLOAK-1758 add-user script

docbook/auth-server-docs/reference/en/en-US/modules/server-installation.xml

@@ -127,6 +127,25 @@ cd <WILDFLY_HOME>/bin
                 </listitem>
             </itemizedlist>
         </para>
+        <section>
+            <title>Admin User</title>
+            <para>
+                To access the admin console you need an account to login. Currently, there's a default account added
+                with the username <literal>admin</literal> and password <literal>admin</literal>. You will be required
+                to change the password on first login. We are planning on removing the built-in account soon and will
+                instead have an initial step to create the user.
+            </para>
+            <para>
+                You can also create a user with the <literal>add-user</literal> script found in <literal>bin</literal>.
+                This script will create a temporary file with the details of the user, which are imported at startup.
+                To add a user with this script run:
+<programlisting><![CDATA[
+bin/add-user.[sh|bat] -r master -u <username> -p <password>
+]]></programlisting>
+                Then restart the server.
+            </para>
+        </section>
+
         <section>
             <title>Relational Database Configuration</title>
             <para>