Remove the code to handle optional address placeholders

Optional address placeholders aren’t a thing for one-off letters any
more, so we can tidy up the code a bit by removing the parts of the flow
that are accounting for them.

app/main/forms.py

@@ -1372,7 +1372,6 @@ def get_placeholder_form_instance(
     placeholder_name,
     dict_to_populate_from,
     template_type,
-    optional_placeholder=False,
     allow_international_phone_numbers=False,
 ):
 
@@ -1389,8 +1388,6 @@ def get_placeholder_form_instance(
             field = international_phone_number(label=placeholder_name)
         else:
             field = uk_mobile_number(label=placeholder_name)
-    elif optional_placeholder:
-        field = StringField(placeholder_name)
     else:
         field = StringField(placeholder_name, validators=[
             DataRequired(message='Cannot be empty')

app/main/views/send.py

@@ -399,7 +399,6 @@ def send_one_off_letter_address(service_id, template_id):
         ),
         template=template,
         form=form,
-        optional_placeholder=False,
         back_link=get_back_link(service_id, template, 0),
         help=False,
         link_to_upload=True,
@@ -478,12 +477,10 @@ def send_test_step(service_id, template_id, step_index):
     ):
         return redirect(url_for('.send_one_off_letter_address', service_id=service_id, template_id=template_id))
 
-    optional_placeholder = (current_placeholder in optional_address_columns)
     form = get_placeholder_form_instance(
         current_placeholder,
         dict_to_populate_from=get_normalised_placeholders_from_session(),
         template_type=template.template_type,
-        optional_placeholder=optional_placeholder,
         allow_international_phone_numbers=current_service.has_permission('international_sms'),
     )
 
@@ -540,7 +537,6 @@ def send_test_step(service_id, template_id, step_index):
         template=template,
         form=form,
         skip_link=skip_link,
-        optional_placeholder=optional_placeholder,
         back_link=back_link,
         help=get_help_argument(),
         link_to_upload=(

app/templates/views/send-test.html

@@ -25,7 +25,6 @@
       <div class="govuk-grid-column-full {% if form.placeholder_value.label.text == 'phone number' %}extra-tracking{% endif %}">
         {{ textbox(
           form.placeholder_value,
-          hint='Optional' if optional_placeholder else None,
           width='1-1',
         ) }}
       </div>

tests/app/main/test_placeholder_form.py

@@ -9,11 +9,11 @@ def test_form_class_not_mutated(app_):
         method='POST',
         data={'placeholder_value': ''}
     ):
-        form1 = get_placeholder_form_instance('name', {}, 'sms', optional_placeholder=False)
-        form2 = get_placeholder_form_instance('city', {}, 'sms', optional_placeholder=True)
+        form1 = get_placeholder_form_instance('name', {}, 'sms')
+        form2 = get_placeholder_form_instance('city', {}, 'sms')
 
         assert not form1.validate_on_submit()
-        assert form2.validate_on_submit()
+        assert not form2.validate_on_submit()
 
         assert str(form1.placeholder_value.label) == '<label for="placeholder_value">name</label>'
         assert str(form2.placeholder_value.label) == '<label for="placeholder_value">city</label>'