add mau_trial_days config param.

only consider users MAU after they've been around N days.
This is an alternative implementation to https://github.com/matrix-org/synapse/pull/3739
as suggested by @neilisfragile, which is much simpler as you just hold off adding
users to the MAU table until they've been active for more than N days.

tests/storage/test_client_ips.py

@@ -59,6 +59,7 @@ class ClientIpStoreTestCase(tests.unittest.TestCase):
     def test_disabled_monthly_active_user(self):
         self.hs.config.limit_usage_by_mau = False
         self.hs.config.max_mau_value = 50
+        self.hs.config.mau_trial_days = 0
         user_id = "@user:server"
         yield self.store.insert_client_ip(
             user_id, "access_token", "ip", "user_agent", "device_id"
@@ -70,6 +71,7 @@ class ClientIpStoreTestCase(tests.unittest.TestCase):
     def test_adding_monthly_active_user_when_full(self):
         self.hs.config.limit_usage_by_mau = True
         self.hs.config.max_mau_value = 50
+        self.hs.config.mau_trial_days = 0
         lots_of_users = 100
         user_id = "@user:server"
 
@@ -86,6 +88,7 @@ class ClientIpStoreTestCase(tests.unittest.TestCase):
     def test_adding_monthly_active_user_when_space(self):
         self.hs.config.limit_usage_by_mau = True
         self.hs.config.max_mau_value = 50
+        self.hs.config.mau_trial_days = 0
         user_id = "@user:server"
         active = yield self.store.user_last_seen_monthly_active(user_id)
         self.assertFalse(active)
@@ -100,6 +103,7 @@ class ClientIpStoreTestCase(tests.unittest.TestCase):
     def test_updating_monthly_active_user_when_space(self):
         self.hs.config.limit_usage_by_mau = True
         self.hs.config.max_mau_value = 50
+        self.hs.config.mau_trial_days = 0
         user_id = "@user:server"
 
         active = yield self.store.user_last_seen_monthly_active(user_id)

tests/storage/test_monthly_active_users.py

@@ -30,6 +30,7 @@ class MonthlyActiveUsersTestCase(tests.unittest.TestCase):
     def setUp(self):
         self.hs = yield setup_test_homeserver(self.addCleanup)
         self.store = self.hs.get_datastore()
+        self.hs.config.mau_trial_days = 0
 
     @defer.inlineCallbacks
     def test_initialise_reserved_users(self):
@@ -105,13 +106,13 @@ class MonthlyActiveUsersTestCase(tests.unittest.TestCase):
         user_id3 = "@user3:server"
 
         result = yield self.store.user_last_seen_monthly_active(user_id1)
-        self.assertFalse(result == 0)
+        self.assertFalse(result)
         yield self.store.upsert_monthly_active_user(user_id1)
         yield self.store.upsert_monthly_active_user(user_id2)
         result = yield self.store.user_last_seen_monthly_active(user_id1)
-        self.assertTrue(result > 0)
+        self.assertTrue(result[0] > 0)
         result = yield self.store.user_last_seen_monthly_active(user_id3)
-        self.assertFalse(result == 0)
+        self.assertFalse(result)
 
     @defer.inlineCallbacks
     def test_reap_monthly_active_users(self):