Allows services to choose if they can send letters

Our support ticket analysis shows that the most common action request
after going live is turning on letters.

We just do this for any team that requests it – there’s no gatekeeping.
So we should just allow people to make the change themselves.

This will be a better experience for our users, and less work for us.
The design of the page replicates roughly what we have for international
text messaging.

app/main/forms.py

@@ -584,6 +584,17 @@ class ServiceLetterContactBlockForm(StripWhitespaceForm):
             )
 
 
+class ServiceSwitchLettersForm(StripWhitespaceForm):
+
+    enabled = RadioField(
+        'Send letters',
+        choices=[
+            ('on', 'On'),
+            ('off', 'Off'),
+        ],
+    )
+
+
 class ServiceBrandingOrg(StripWhitespaceForm):
 
     def __init__(self, organisations=[], *args, **kwargs):

app/main/views/service_settings.py

@@ -35,6 +35,7 @@ from app.main.forms import (
     FreeSMSAllowance,
     ServiceEditInboundNumberForm,
     SMSPrefixForm,
+    ServiceSwitchLettersForm,
 )
 from app import user_api_client, current_service, organisations_client, inbound_number_client, billing_api_client
 from notifications_utils.formatters import formatted_list
@@ -502,12 +503,25 @@ def service_set_inbound_sms(service_id):
     )
 
 
-@main.route("/services/<service_id>/service-settings/set-letters", methods=['GET'])
+@main.route("/services/<service_id>/service-settings/set-letters", methods=['GET', 'POST'])
 @login_required
 @user_has_permissions('manage_settings', admin_override=True)
 def service_set_letters(service_id):
+    form = ServiceSwitchLettersForm(
+        enabled='on' if 'letter' in current_service['permissions'] else 'off'
+    )
+    if form.validate_on_submit():
+        force_service_permission(
+            service_id,
+            'letter',
+            on=(form.enabled.data == 'on'),
+        )
+        return redirect(
+            url_for(".service_settings", service_id=service_id)
+        )
     return render_template(
         'views/service-settings/set-letters.html',
+        form=form,
     )
 
 

app/templates/views/pricing.html

@@ -87,7 +87,7 @@
 
     </details>
 
-    <h2 class="heading-medium">Letters</h2>
+    <h2 class="heading-medium" id="letters">Letters</h2>
     <p>The cost of sending a letter depends on how many sheets of paper you need.</p>
     <div class="bottom-gutter-3-2">
       {% call mapping_table(

app/templates/views/service-settings/set-letters.html

@@ -1,34 +1,26 @@
 {% extends "withnav_template.html" %}
-{% from "components/textbox.html" import textbox %}
+{% from "components/radios.html" import radios %}
 {% from "components/page-footer.html" import page_footer %}
 
 {% block service_page_title %}
-  Text message sender
+  Send letters
 {% endblock %}
 
 {% block maincolumn_content %}
 
   <div class="grid-row">
     <div class="column-five-sixths">
-      <h1 class="heading-large">Letters</h1>
-      {% if 'letter' in current_service.permissions %} 
-        <p>
-          Your service can send letters.
-        </p>
-        <p>
-          If you want to stop your service from sending letters,
-          <a href="{{ url_for('.support') }}">get in touch with the GOV.UK Notify team</a>.
-        </p>
-      {% else %}
-        <p>
-          Using GOV.UK Notify to send letters is an invitation&#8209;only feature.
-        </p>
-        <p>
-          If you want to try it out,
-          <a href="{{ url_for('.support') }}">get in touch with the GOV.UK Notify team</a>.
-        </p>
-      {% endif %}
+      <h1 class="heading-large">Send letters</h1>
+      <p>
+        It costs between 30p and 45p to send a letter using Notify.
+      </p>
+      <p>
+        See <a href="{{ url_for(".pricing", _anchor="letters") }}">pricing</a> for the list
+        of rates.
+      </p>
+      {{ radios(form.enabled) }}
       {{ page_footer(
+        'Save',
         back_link=url_for('.service_settings', service_id=current_service.id),
         back_link_text='Back to settings'
       ) }}

tests/app/main/views/test_service_settings.py

@@ -1557,40 +1557,50 @@ def test_should_set_sms_allowance(
     )
 
 
+@pytest.mark.parametrize((
+    'expected_initial_value,'
+    'posted_value,'
+    'initial_permissions,'
+    'expected_updated_permissions'
+), [
+    ('off', 'on', ['email', 'sms'], ['email', 'sms', 'letter']),
+    ('on', 'off', ['email', 'sms', 'letter'], ['email', 'sms']),
+])
 def test_switch_service_enable_letters(
-    logged_in_platform_admin_client,
+    client_request,
     service_one,
     mocker,
+    expected_initial_value,
+    posted_value,
+    initial_permissions,
+    expected_updated_permissions,
 ):
     mocked_fn = mocker.patch('app.service_api_client.update_service_with_properties', return_value=service_one)
+    service_one['permissions'] = initial_permissions
 
-    response = logged_in_platform_admin_client.get(
-        url_for('main.service_switch_can_send_letters', service_id=service_one['id'])
+    page = client_request.get(
+        'main.service_set_letters',
+        service_id=service_one['id'],
     )
 
-    assert response.status_code == 302
-    assert response.location == url_for('main.service_settings', service_id=service_one['id'], _external=True)
-    assert 'letter' in mocked_fn.call_args[0][1]['permissions']
+    assert page.select_one('input[checked]')['value'] == expected_initial_value
+    assert len(page.select('input[checked]')) == 1
+
+    client_request.post(
+        'main.service_set_letters',
+        service_id=service_one['id'],
+        _data={'enabled': posted_value},
+        _expected_redirect=url_for(
+            'main.service_settings',
+            service_id=service_one['id'],
+            _external=True
+        )
+    )
+
+    assert set(mocked_fn.call_args[0][1]['permissions']) == set(expected_updated_permissions)
     assert mocked_fn.call_args[0][0] == service_one['id']
 
 
-def test_switch_service_disable_letters(
-    logged_in_platform_admin_client,
-    service_one,
-    mocker,
-):
-    service_one['permissions'] = ['letter']
-    mocked_fn = mocker.patch('app.service_api_client.update_service_with_properties', return_value=service_one)
-
-    response = logged_in_platform_admin_client.get(
-        url_for('main.service_switch_can_send_letters', service_id=service_one['id'])
-    )
-
-    assert response.status_code == 302
-    assert response.location == url_for('main.service_settings', service_id=service_one['id'], _external=True)
-    assert mocked_fn.call_args == call(service_one['id'], {"permissions": []})
-
-
 @pytest.mark.parametrize('permissions, expected_checked', [
     (['international_sms'], 'on'),
     ([''], 'off'),
@@ -1802,21 +1812,6 @@ def test_cant_resume_active_service(
 
 
 @pytest.mark.parametrize('endpoint, permissions, expected_p', [
-    (
-        'main.service_set_letters',
-        [],
-        (
-            'Using GOV.UK Notify to send letters is an invitation‑only '
-            'feature.'
-        )
-    ),
-    (
-        'main.service_set_letters',
-        ['letter'],
-        (
-            'Your service can send letters.'
-        )
-    ),
     (
         'main.service_set_inbound_sms',
         ['sms'],