ephemeral events: add support for MSC2409 ephemeral events

Closes #19

config/appservice.go

@@ -17,6 +17,8 @@ type appservice struct {
 
 	Database database `yaml:"database"`
 
+	EphemeralEvents bool `yaml:"ephemeral_events"`
+
 	ASToken string `yaml:"as_token"`
 	HSToken string `yaml:"hs_token"`
 }

config/registration.go

@@ -10,6 +10,7 @@ import (
 func (cfg *Config) CopyToRegistration(registration *as.Registration) error {
 	registration.ID = cfg.Appservice.ID
 	registration.URL = cfg.Appservice.Address
+	registration.EphemeralEvents = cfg.Appservice.EphemeralEvents
 
 	falseVal := false
 	registration.RateLimited = &falseVal

example-config.yaml

@@ -52,6 +52,11 @@ appservice:
       displayname: Discord bridge bot
       avatar: mxc://beeper.com/222332ba2b197e57b73ef2db236232db79af62d0
 
+    # Whether or not to receive ephemeral events via appservice transactions.
+    # Requires MSC2409 support (i.e. Synapse 1.22+).
+    # You should disable bridge -> sync_with_custom_puppets when this is enabled.
+    ephemeral_events: false
+
     # Authentication tokens for AS <-> HS communication. Autogenerated; do not modify.
     as_token: "This value is generated when generating the registration"
     hs_token: "This value is generated when generating the registration"