make dao_get_jobs_by_service_id paginated

it can return a pretty long list, especially when we run lots of
smoke tests, so make it accept pagination parameters, and return
a pagination object

app/dao/jobs_dao.py

@@ -1,10 +1,11 @@
-from datetime import date, timedelta, datetime
-from sqlalchemy import desc, asc, cast, Date as sql_date
+from datetime import datetime
+
+from sqlalchemy import func, desc, asc, cast, Date as sql_date
+
 from app import db
 from app.dao import days_ago
 from app.models import Job, NotificationHistory, JOB_STATUS_SCHEDULED
 from app.statsd_decorators import statsd
-from sqlalchemy import func, asc
 
 
 @statsd(namespace="dao")
@@ -26,11 +27,14 @@ def dao_get_job_by_service_id_and_job_id(service_id, job_id):
     return Job.query.filter_by(service_id=service_id, id=job_id).one()
 
 
-def dao_get_jobs_by_service_id(service_id, limit_days=None):
+def dao_get_jobs_by_service_id(service_id, limit_days=None, page=1, page_size=50):
     query_filter = [Job.service_id == service_id]
     if limit_days is not None:
         query_filter.append(cast(Job.created_at, sql_date) >= days_ago(limit_days))
-    return Job.query.filter(*query_filter).order_by(desc(Job.created_at)).all()
+    return Job.query \
+        .filter(*query_filter) \
+        .order_by(desc(Job.created_at)) \
+        .paginate(page=page, per_page=page_size)
 
 
 def dao_get_job_by_id(job_id):