Cache service data retention in Redis

Adds caching for service data retention. This removes separate API
client methods to retrieve individual data retention records by id
or type in favor of a single method that fetches and caches all
retention settings configured for the service. This makes it much
easier to invalidate cache when settings change.

Lookup by id or type is provided by helper methods in the service
model.

app/main/views/jobs.py

@@ -226,8 +226,8 @@ def get_notifications(service_id, message_type, status_override=None):
     service_data_retention_days = None
 
     if message_type is not None:
-        service_data_retention_days = service_api_client.get_service_data_retention_by_notification_type(
-            service_id, message_type
+        service_data_retention_days = current_service.get_data_retention_by_type(
+            message_type
         ).get('days_of_retention', current_app.config['ACTIVITY_STATS_LIMIT_DAYS'])
 
     if request.path.endswith('csv') and current_user.has_permissions('view_activity'):
@@ -406,8 +406,8 @@ def get_job_partials(job, template):
             counts=_get_job_counts(job),
             status=filter_args['status']
         )
-    service_data_retention_days = service_api_client.get_service_data_retention_by_notification_type(
-        current_service.id, template['template_type']
+    service_data_retention_days = current_service.get_data_retention_by_type(
+        template['template_type']
     ).get('days_of_retention', current_app.config['ACTIVITY_STATS_LIMIT_DAYS'])
 
     return {

app/main/views/notifications.py

@@ -30,7 +30,6 @@ from app import (
     format_date_numeric,
     job_api_client,
     notification_api_client,
-    service_api_client,
 )
 from app.main import main
 from app.notify_client.api_key_api_client import KEY_TYPE_TEST
@@ -198,8 +197,8 @@ def download_notifications_csv(service_id):
     filter_args = parse_filter_args(request.args)
     filter_args['status'] = set_status_filters(filter_args)
 
-    service_data_retention_days = service_api_client.get_service_data_retention_by_notification_type(
-        service_id, filter_args.get('message_type')[0]
+    service_data_retention_days = current_service.get_data_retention_by_type(
+        filter_args.get('message_type')[0]
     ).get('days_of_retention', current_app.config['ACTIVITY_STATS_LIMIT_DAYS'])
     return Response(
         stream_with_context(