Check CSV files match the template

This commit adds a first stab at checking whether a CSV file has the right
data to fill the placeholders.

The UI is very much first bash, but I’d like to get this merged and see how it
feels. The main thing is that we’ve got all the bit in place now to do this
logic.

app/main/views/sms.py

@@ -14,11 +14,10 @@ from flask import (
     flash,
     abort,
     session,
-    current_app,
-    Markup
+    current_app
 )
 
-from flask_login import login_required
+from flask_login import login_required, current_user
 from werkzeug import secure_filename
 from notifications_python_client.errors import HTTPError
 from utils.template import Template
@@ -72,10 +71,19 @@ def send_sms(service_id, template_id):
        templates_dao.get_service_template_or_404(service_id, template_id)['data']
     )
 
+    example_data = [dict(
+        phone=current_user.mobile_number,
+        **{
+            header: "test {}".format(header) for header in template.placeholders
+        }
+    )]
+
     return render_template(
         'views/send-sms.html',
         template=template,
-        column_headers=['phone number'] + template.placeholders_as_markup,
+        column_headers=['phone'] + template.placeholders_as_markup,
+        placeholders=template.placeholders,
+        example_data=example_data,
         form=form,
         service_id=service_id
     )
@@ -85,10 +93,11 @@ def send_sms(service_id, template_id):
 @login_required
 def get_example_csv(service_id, template_id):
     template = templates_dao.get_service_template_or_404(service_id, template_id)['data']
+    placeholders = list(Template(template).placeholders)
     output = io.StringIO()
-    csv.writer(output).writerow(
-        ['phone number'] + Template(template).list_placeholders
-    )
+    writer = csv.writer(output)
+    writer.writerow(['phone'] + placeholders)
+    writer.writerow([current_user.mobile_number] + ["test {}".format(header) for header in placeholders])
 
     return(output.getvalue(), 200, {'Content-Type': 'text/csv; charset=utf-8'})
 
@@ -116,7 +125,8 @@ def check_sms(service_id, upload_id):
             template=template,
             column_headers=['phone number'] + template.placeholders_as_markup,
             original_file_name=upload_data.get('original_file_name'),
-            service_id=service_id
+            service_id=service_id,
+            form=CsvUploadForm()
         )
     elif request.method == 'POST':
         upload_data = session['upload_data']