Check if a private property of a resource is set without using it.

[mmzeeman]

Zotonic version

1.0.0.rc15

Description

It is sometimes handy to check if a resource has a private property set, without the ability to actually use the property.

For instance... Checking if a users has an email adres setup, so you can display a contact form. Because the email field is private it is currently not possible to write

{% if id.email %}
   {# show contact form #}
{% endif %}

(Via @DorienD)

Proposal

Add something like this:

{% if id.has_property.email %}
  {# show contact form #}
{% endif %}

To make it possible to check if a private property is set, without the possibility to actually use the property. Could also be done via a separate model.