refactor performance platform code

so that it doesn't appear generic when it's actually specific to
sending the daily notification totals. To do this, split it out into a
separate performance_platform directory, containing the business logic,
and make the performance_platform_client incredibly thin - all it
handles is adding ids to payloads, and sending stats.

Also, some changes to the config (not all done yet) since there is one
token per endpoint, not one for the whole platform as we'd previously
coded

tests/app/performance_platform/test_total_sent_notifications.py

@@ -0,0 +1,77 @@
+from datetime import datetime
+from functools import partial
+
+from freezegun import freeze_time
+
+from app.utils import get_midnight_for_day_before
+from app.performance_platform.total_sent_notifications import(
+    send_total_notifications_sent_for_day_stats,
+    get_total_sent_notifications_yesterday
+)
+
+from tests.app.conftest import (
+    sample_notification_history as create_notification_history
+)
+
+
+def test_send_total_notifications_sent_for_day_stats_stats_creates_correct_call(mocker, client):
+    send_stats = mocker.patch('app.performance_platform.total_sent_notifications.performance_platform_client.send_stats_to_performance_platform')  # noqa
+
+    send_total_notifications_sent_for_day_stats(
+        date=datetime(2016, 10, 15, 23, 0, 0),
+        channel='sms',
+        count=142,
+        period='day'
+    )
+
+    assert send_stats.call_count == 1
+    assert send_stats.call_args[1]['dataset'] == 'notifications'
+
+    request_args = send_stats.call_args[1]['payload']
+    assert request_args['dataType'] == 'notifications'
+    assert request_args['service'] == 'govuk-notify'
+    assert request_args['period'] == 'day'
+    assert request_args['channel'] == 'sms'
+    assert request_args['_timestamp'] == '2016-10-16T00:00:00'
+    assert request_args['count'] == 142
+    expected_base64_id = 'MjAxNi0xMC0xNlQwMDowMDowMGdvdnVrLW5vdGlmeXNtc25vdGlmaWNhdGlvbnNkYXk='
+    assert request_args['_id'] == expected_base64_id
+
+
+@freeze_time("2016-01-11 12:30:00")
+def test_get_total_sent_notifications_yesterday_returns_expected_totals_dict(
+    notify_db,
+    notify_db_session,
+    sample_template
+):
+    notification_history = partial(
+        create_notification_history,
+        notify_db,
+        notify_db_session,
+        sample_template,
+        status='delivered'
+    )
+
+    notification_history(notification_type='email')
+    notification_history(notification_type='sms')
+
+    # Create some notifications for the day before
+    yesterday = datetime(2016, 1, 10, 15, 30, 0, 0)
+    with freeze_time(yesterday):
+        notification_history(notification_type='sms')
+        notification_history(notification_type='sms')
+        notification_history(notification_type='email')
+        notification_history(notification_type='email')
+        notification_history(notification_type='email')
+
+    total_count_dict = get_total_sent_notifications_yesterday()
+
+    assert total_count_dict == {
+        "start_date": get_midnight_for_day_before(datetime.utcnow()),
+        "email": {
+            "count": 3
+        },
+        "sms": {
+            "count": 2
+        }
+    }