Allow services to turn international SMS on/off

We didn’t make this self-service before because the pricing information
wasn’t published (ie we had to send it to services that asked for it).

Now that we publish pricing information in the app, there’s no reason
why services can’t make an informed decision about whether they want
international SMS or not.

So this commit:
- removes the platform admin button
- adds some radio buttons that our users can click with their mice

app/main/views/service_settings.py

@@ -32,7 +32,9 @@ from app.main.forms import (
     ServiceLetterContactBlock,
     ServiceBrandingOrg,
     LetterBranding,
-    ServiceInboundApiForm)
+    ServiceInboundApiForm,
+    InternationalSMSForm,
+)
 from app import user_api_client, current_service, organisations_client, inbound_number_client
 
 
@@ -222,13 +224,22 @@ def service_switch_research_mode(service_id):
     return redirect(url_for('.service_settings', service_id=service_id))
 
 
-def switch_service_permissions(service_id, permission, sms_sender=None):
+def switch_service_permissions(service_id, permission, sms_sender=None, force=None):
+
     permissions = current_service['permissions'].copy()
-    if permission in permissions:
-        permissions.remove(permission)
+
+    if force is None:
+        if permission in permissions:
+            permissions.remove(permission)
+        else:
+            permissions.append(permission)
     else:
-        permissions.append(permission)
-    current_service['permissions'] = permissions
+        if force is True:
+            permissions.append(permission)
+        elif force is False and permission in permissions:
+            permissions.remove(permission)
+
+    current_service['permissions'] = list(set(permissions))
 
     data = {'permissions': permissions}
     if sms_sender:
@@ -423,12 +434,25 @@ def service_set_sms(service_id):
     )
 
 
-@main.route("/services/<service_id>/service-settings/set-international-sms", methods=['GET'])
+@main.route("/services/<service_id>/service-settings/set-international-sms", methods=['GET', 'POST'])
 @login_required
 @user_has_permissions('manage_settings', admin_override=True)
 def service_set_international_sms(service_id):
+    form = InternationalSMSForm(
+        enabled='on' if 'international_sms' in current_service['permissions'] else 'off'
+    )
+    if form.validate_on_submit():
+        switch_service_permissions(
+            service_id,
+            'international_sms',
+            force=False if form.enabled.data == 'off' else True,
+        )
+        return redirect(
+            url_for(".service_settings", service_id=service_id)
+        )
     return render_template(
         'views/service-settings/set-international-sms.html',
+        form=form,
     )