After investigations, commit the proposed patch by kklimonda presented with the
following introduction :
cm/templates/site/login_form.html template uses a relative url for the form action, which seems to break deployment in the subfolder when trailing slash is missing (the form redirects to the upper folder breaking login). Using {% url login %} (as in the attached patch) instead would fix the issue.
{% extends "email/base_email.txt" %}{% load i18n %}{% block content %}{% if note %}{{ note }}{% endif %}
{% blocktrans with CONF.workspace_name as workspace_name %}You've been invited to join the workspace {{ workspace_name }}.{% endblocktrans %}
{% blocktrans %}Click the following link to complete your registration and access the workspace:{% endblocktrans %}
{{ CONF.site_url }}{{ activate_url }}{% endblock %}