Stable support for MSC4115-style membership properties (#725)

* Move MSC4115 test to main CSAPI suite

This is stable now.

* Switch membership property to stable identifier

tests/msc4115/msc4115_test.go → tests/csapi/membership_on_events_test.go

@@ -1,4 +1,4 @@
-package tests
+package csapi_tests
 
 import (
 	"github.com/matrix-org/complement/b"
@@ -10,11 +10,11 @@ import (
 	"github.com/matrix-org/complement/helpers"
 )
 
-// MSC4115: membership information on events
+// Membership information on events served to clients, as specified in MSC4115.
 //
-// Alice sends one message before bob joins, then one after. Bob reads both messages, and checks the membership state
+// Alice sends one message before Bob joins, then one after. Bob reads both messages, and checks the membership state
 // on each.
-func TestMSC4115(t *testing.T) {
+func TestMembershipOnEvents(t *testing.T) {
 	runtime.SkipIf(t, runtime.Dendrite) // not yet implemented
 
 	deployment := complement.Deploy(t, 1)
@@ -52,7 +52,7 @@ func TestMSC4115(t *testing.T) {
 		if ev.Get("type").Str == "m.room.member" && ev.Get("state_key").Str == bob.UserID {
 			haveSeenJoin = true
 		}
-		membership := ev.Get("unsigned." + client.GjsonEscape("io.element.msc4115.membership")).Str
+		membership := ev.Get("unsigned.membership").Str
 		expectedMembership := "leave"
 		if haveSeenJoin {
 			expectedMembership = "join"