Use a macro for form tags

This will stop us repeatedly forgetting to add `novalidate` and
`autocomplete='off'` to our forms (which is how most of them are set
up).

It uses sensible defaults, based on how we most-commonly configure
forms:
- most of our forms are `post`ed (but this can be overridden)
- `autocomplete` should only be enabled where it makes sense, otherwise
  it’s more annoying than useful (but this can be overriden)
- we should never be using HTML5 form validation because our own error
  styles and messages are better

app/templates/views/support/ask-question-give-feedback.html

@@ -1,6 +1,7 @@
 {% extends "withoutnav_template.html" %}
 {% from "components/textbox.html" import textbox %}
 {% from "components/page-footer.html" import page_footer %}
+{% from "components/form.html" import form_wrapper %}
 
 {% block per_page_title %}
   Ask a question or give feedback
@@ -13,7 +14,7 @@
     </h1>
     <div class="grid-row">
       <div class="column-two-thirds">
-        <form method="post" autocomplete="off" novalidate>
+        {% call form_wrapper() %}
             {{ textbox(form.feedback, width='1-1', hint='', rows=10) }}
             {% if not current_user.is_authenticated %}
               <h3 class="heading-medium">Do you want a reply?</h3>
@@ -28,7 +29,7 @@
               secondary_link=url_for('.support'),
               secondary_link_text='Back to support',
             ) }}
-        </form>
+        {% endcall %}
       </div>
     </div>
 

app/templates/views/support/index.html

@@ -1,6 +1,7 @@
 {% extends "withoutnav_template.html" %}
 {% from "components/radios.html" import radios %}
 {% from "components/page-footer.html" import page_footer %}
+{% from "components/form.html" import form_wrapper %}
 
 {% block per_page_title %}
   Support
@@ -13,10 +14,11 @@
 
     <h1 class="heading-large">Support</h1>
 
-    <form method="post" class="bottom-gutter-2">
+    {% call form_wrapper(class="bottom-gutter-2") %}
       {{ radios(form.support_type) }}
       {{ page_footer('Continue') }}
-    </form>
+    {% endcall %}
+
     <p>If something’s wrong, you can <a href="https://status.notifications.service.gov.uk/"> check the GOV.UK Notify system status page</a> to see if we’re already aware of it.</p>
 
     <h2 class="heading-medium">24-hour support</h2>

app/templates/views/support/report-problem.html

@@ -2,6 +2,7 @@
 {% from "components/checkbox.html" import checkbox %}
 {% from "components/textbox.html" import textbox %}
 {% from "components/page-footer.html" import page_footer %}
+{% from "components/form.html" import form_wrapper %}
 
 {% block per_page_title %}
   Report a problem
@@ -20,7 +21,7 @@
             page to see if there are any known issues with GOV.UK Notify.
           </p>
         </div>
-        <form method="post" autocomplete="off" novalidate>
+        {% call form_wrapper() %}
             {{ textbox(form.feedback, width='1-1', hint='', rows=10) }}
             {% if not current_user.is_authenticated %}
               {{ textbox(form.name, width='1-1') }}
@@ -33,7 +34,7 @@
               secondary_link=url_for('.support'),
               secondary_link_text='Back to support',
             ) }}
-        </form>
+        {% endcall %}
       </div>
     </div>
 

app/templates/views/support/triage.html

@@ -1,6 +1,7 @@
 {% extends "withoutnav_template.html" %}
 {% from "components/radios.html" import radios %}
 {% from "components/page-footer.html" import page_footer %}
+{% from "components/form.html" import form_wrapper %}
 
 {% block per_page_title %}
   Feedback
@@ -13,10 +14,10 @@
       <h1 class="heading-large">
         Report a problem
       </h1>
-      <form method="post">
+      {% call form_wrapper() %}
         {{ radios(form.severe) }}
         {{ page_footer('Continue') }}
-      </form>
+      {% endcall %}
       <h2 class="heading-small">
         It’s only an emergency if:
       </h2>