providers/saml: add custom help text for templates, add docs for User Object reference

passbook/sources/ldap/templates/ldap/property_mapping_form.html

@@ -0,0 +1,18 @@
+{% extends "generic/form.html" %}
+
+{% load i18n %}
+
+{% block beneath_form %}
+<div class="form-group ">
+    <label class="col-sm-2 control-label" for="friendly_name-2">
+    </label>
+    <div class="col-sm-10">
+        <p>
+            Expression using <a href="https://jinja.palletsprojects.com/en/2.11.x/templates/">Jinja</a>. Following variables are available:
+            <ul>
+                <li><code>ldap</code>: A Dictionary of all values retrieved from LDAP.</li>
+            </ul>
+        </p>
+    </div>
+</div>
+{% endblock %}