Add `mau_appservice_trial_days` config (#12619)

* Add mau_appservice_trial_days

* Add a test

* Tweaks

* changelog

* Ensure we sync after the delay

* Fix types

* Add config statement

* Fix test

* Reinstate logging that got removed

* Fix feature name

2 files changed, 14 insertions, 2 deletions

diff --git a/synapse/config/server.py b/synapse/config/server.py
index b6cd326416..1e709c7cf5 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -413,6 +413,7 @@ class ServerConfig(Config):
         )
 
         self.mau_trial_days = config.get("mau_trial_days", 0)
+        self.mau_appservice_trial_days = config.get("mau_appservice_trial_days", {})
         self.mau_limit_alerting = config.get("mau_limit_alerting", True)
 
         # How long to keep redacted events in the database in unredacted form
@@ -1105,6 +1106,11 @@ class ServerConfig(Config):
         # sign up in a short space of time never to return after their initial
         # session.
         #
+        # The option `mau_appservice_trial_days` is similar to `mau_trial_days`, but
+        # applies a different trial number if the user was registered by an appservice.
+        # A value of 0 means no trial days are applied. Appservices not listed in this
+        # dictionary use the value of `mau_trial_days` instead.
+        #
         # 'mau_limit_alerting' is a means of limiting client side alerting
         # should the mau limit be reached. This is useful for small instances
         # where the admin has 5 mau seats (say) for 5 specific people and no
@@ -1115,6 +1121,8 @@ class ServerConfig(Config):
         #max_mau_value: 50
         #mau_trial_days: 2
         #mau_limit_alerting: false
+        #mau_appservice_trial_days:
+        #  "appservice-id": 1
 
         # If enabled, the metrics for the number of monthly active users will
         # be populated, however no one will be limited. If limit_usage_by_mau
diff --git a/synapse/storage/databases/main/registration.py b/synapse/storage/databases/main/registration.py
index d43163c27c..4991360b70 100644
--- a/synapse/storage/databases/main/registration.py
+++ b/synapse/storage/databases/main/registration.py
@@ -215,7 +215,8 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
 
     async def is_trial_user(self, user_id: str) -> bool:
         """Checks if user is in the "trial" period, i.e. within the first
-        N days of registration defined by `mau_trial_days` config
+        N days of registration defined by `mau_trial_days` config or the
+        `mau_appservice_trial_days` config.
 
         Args:
             user_id: The user to check for trial status.
@@ -226,7 +227,10 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
             return False
 
         now = self._clock.time_msec()
-        trial_duration_ms = self.config.server.mau_trial_days * 24 * 60 * 60 * 1000
+        days = self.config.server.mau_appservice_trial_days.get(
+            info["appservice_id"], self.config.server.mau_trial_days
+        )
+        trial_duration_ms = days * 24 * 60 * 60 * 1000
         is_trial = (now - info["creation_ts"] * 1000) < trial_duration_ms
         return is_trial