Always use 12h times

The GOV.UK content style guide says:

> - 5:30pm (not 1730hrs)
> - midnight (not 00:00)
> - midday (not 12 noon, noon or 12pm)

This commit changes all times to be 12h not 24h, and adds a special case
for when a time is exactly 12:00am or 12:00pm.

app/__init__.py

@@ -105,6 +105,7 @@ def create_app():
 
     application.add_template_filter(nl2br)
     application.add_template_filter(format_datetime)
+    application.add_template_filter(format_datetime_24h)
     application.add_template_filter(format_datetime_normal)
     application.add_template_filter(format_datetime_short)
     application.add_template_filter(format_time)
@@ -200,19 +201,41 @@ def gmt_timezones(date):
 
 
 def format_datetime(date):
-    return gmt_timezones(date).strftime('%A %d %B %Y at %H:%M')
+    return '{} at {}'.format(
+        format_date(date),
+        format_time(date)
+    )
+
+
+def format_datetime_24h(date):
+    return '{} at {}'.format(
+        format_date(date),
+        gmt_timezones(date).strftime('%H:%M')
+    )
 
 
 def format_datetime_normal(date):
-    return gmt_timezones(date).strftime('%d %B %Y at %H:%M').lstrip('0')
+    return '{} at {}'.format(
+        format_date_normal(date),
+        format_time(date)
+    )
 
 
 def format_datetime_short(date):
-    return gmt_timezones(date).strftime('%d %B at %H:%M').lstrip('0')
+    return '{} at {}'.format(
+        format_date_short(date),
+        format_time(date)
+    )
 
 
 def format_time(date):
-    return gmt_timezones(date).strftime('%H:%M')
+    return {
+        '12:00AM': 'Midnight',
+        '12:00PM': 'Midday'
+    }.get(
+        gmt_timezones(date).strftime('%-I:%M%p'),
+        gmt_timezones(date).strftime('%-I:%M%p')
+    ).lower()
 
 
 def format_date(date):

app/utils.py

@@ -89,7 +89,7 @@ def get_errors_for_csv(recipients, template_type):
 
 
 def generate_notifications_csv(json_list):
-    from app import format_datetime, format_notification_status
+    from app import format_datetime_24h, format_notification_status
     content = StringIO()
     retval = None
     with content as csvfile:
@@ -103,7 +103,7 @@ def generate_notifications_csv(json_list):
                 x['template']['template_type'],
                 x['job']['original_file_name'] if x['job'] else '',
                 format_notification_status(x['status'], x['template']['template_type']),
-                format_datetime(x['created_at'])])
+                format_datetime_24h(x['created_at'])])
         retval = content.getvalue()
     return retval