Add three new columns to job_statistics for sent, delivered and failed.

A job only ever has one notification type.
This is the first deploy, where the columns are added and populated.

Next a data migration will happen to populate these new columns for the older jobs that do not have the values set.
Then we stop populating the old columns and remove them.
This refactoring of the table structure will make the queries to the table much easier to handle.

app/dao/statistics_dao.py

@@ -60,7 +60,10 @@ def timeout_job_counts(notifications_type, timeout_start):
         ).update({
             sent: sent_count,
             failed: failed_count,
-            delivered: delivered_count
+            delivered: delivered_count,
+            'sent': sent_count,
+            'delivered': delivered_count,
+            'failed': failed_count
         }, synchronize_session=False)
     return total_updated
 
@@ -87,11 +90,13 @@ def create_or_update_job_sending_statistics(notification):
 @transactional
 def __update_job_stats_sent_count(notification):
     column = columns(notification.notification_type, 'sent')
+    new_column = 'sent'
 
     return db.session.query(JobStatistics).filter_by(
         job_id=notification.job_id,
     ).update({
-        column: column + 1
+        column: column + 1,
+        new_column: column + 1
     })
 
 
@@ -102,7 +107,8 @@ def __insert_job_stats(notification):
         emails_sent=1 if notification.notification_type == EMAIL_TYPE else 0,
         sms_sent=1 if notification.notification_type == SMS_TYPE else 0,
         letters_sent=1 if notification.notification_type == LETTER_TYPE else 0,
-        updated_at=datetime.utcnow()
+        updated_at=datetime.utcnow(),
+        sent=1
     )
     db.session.add(stats)
 
@@ -131,10 +137,12 @@ def columns(notification_type, status):
 def update_job_stats_outcome_count(notification):
     if notification.status in NOTIFICATION_STATUS_TYPES_FAILED:
         column = columns(notification.notification_type, 'failed')
+        new_column = 'failed'
 
     elif notification.status in [NOTIFICATION_DELIVERED,
                                  NOTIFICATION_SENT] and notification.notification_type != LETTER_TYPE:
         column = columns(notification.notification_type, 'delivered')
+        new_column = 'delivered'
 
     else:
         column = None
@@ -143,7 +151,8 @@ def update_job_stats_outcome_count(notification):
         return db.session.query(JobStatistics).filter_by(
             job_id=notification.job_id,
         ).update({
-            column: column + 1
+            column: column + 1,
+            new_column: column + 1
         })
     else:
         return 0