Add a page to pick a template to reply with

If your service is receiving inbound messages, you might want to reply
to them. Without an API integration, the only way to do this is by doing
the send one off flow. But currently there is no direct link from the
page which shows the inbound messages.

So this commit:
- adds a link to a new page…
- …which shows the available (ie only text message) templates with which
  you can reply

app/main/views/conversation.py

@@ -7,6 +7,7 @@ from flask_login import login_required
 from notifications_utils.recipients import format_phone_number_human_readable
 from notifications_utils.template import SMSPreviewTemplate
 from app.main import main
+from app.main.forms import SearchTemplatesForm
 from app.utils import user_has_permissions
 from app import notification_api_client, service_api_client
 from notifications_python_client.errors import HTTPError
@@ -24,6 +25,7 @@ def conversation(service_id, notification_id):
         user_number=user_number,
         partials=get_conversation_partials(service_id, user_number),
         updates_url=url_for('.conversation_updates', service_id=service_id, notification_id=notification_id),
+        notification_id=notification_id,
     )
 
 
@@ -38,6 +40,29 @@ def conversation_updates(service_id, notification_id):
     ))
 
 
+@main.route("/services/<service_id>/conversation/<notification_id>/reply-with")
+@login_required
+@user_has_permissions('send_texts', admin_override=True)
+def conversation_reply(
+    service_id,
+    notification_id,
+):
+
+    templates = [
+        template
+        for template in service_api_client.get_service_templates(service_id)['data']
+        if template['template_type'] == 'sms'
+    ]
+
+    return render_template(
+        'views/templates/choose-reply.html',
+        templates=templates,
+        show_search_box=(len(templates) > 7),
+        template_type='sms',
+        search_form=SearchTemplatesForm(),
+    )
+
+
 def get_conversation_partials(service_id, user_number):
 
     return {