feat: added get_profile_url function to get the profile url in templates

This takes care of generating the correct profile URL depending on the
`profile_url_prefix` setting.

Issue #192

community/templates/discussions/reply_card.html

@@ -3,7 +3,7 @@
   <div class="d-flex align-items-center muted-text">
     {% set member = frappe.get_doc("User", reply.owner) %}
     {{ widgets.Avatar(member=member, avatar_class="avatar-small")}}
-    <a class="button-links ml-2" href="/user/{{ member.username }}">
+    <a class="button-links ml-2" href="{{ get_profile_url(member.username) }}">
       {{ member.full_name }}
     </a>
     <div class="ml-2 frappe-timestamp" data-timestamp="{{ reply.creation }}"> just now </div>