Form tag doesn't include the form.id

Issue

When creating a form such as

{% form 'customer', id: 'ContactFooter' %}
  <span>{{ form.id }}</span>
  [...rest of content...]
{% endform %}

the form.id is nil

Expected

The form object id should be the id of the submitted form and be available within the form. This is especially useful when you might have multiple forms on the page and you want to use form.errors or form.posted_successfully?. Currently, you cannot identify which form actually has the errors. If you try to use those properties, both forms display errors. It would be awesome, if you could do something like:

{% form 'customer', id: 'SomeOtherForm' %}
  {% if form.errors and form.id == 'SomeOtherForm' %}
  [...errors for SomeOtherForm...]
  {% endif %}
{% endform %}


[...more content on the same page...]

{% form 'customer', id: 'ContactFooter' %}
  {% if form.errors and form.id == 'ContactFooter' %}
  [...errors for ContactFooter...]
  {% endif %}
{% endform %}

Discussion

Is having form.id always equal to nil expected behaviour?

Start with the form tag and the form object behavior shown in the issue, tracing how the supplied id is handled inside the form block. Add coverage for multiple forms and verify that form.id reflects each tag's id and allows errors or success state to be distinguished.