fix: proper sending of join URL and removing server timestamp in proto parsing

libsession/src/main/java/org/session/libsession/messaging/open_groups/OpenGroupV2.kt

@@ -39,7 +39,7 @@ data class OpenGroupV2(
 
     }
 
-    fun toJoinUrl(): String = "$server/$id?public_key=$publicKey"
+    fun toJoinUrl(): String = "$server/$room?public_key=$publicKey"
 
     fun toJson(): Map<String,String> = mapOf(
             "room" to room,

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/pollers/OpenGroupV2Poller.kt

@@ -97,7 +97,6 @@ class OpenGroupV2Poller(private val openGroups: List<OpenGroupV2>, private val e
                 builder.source = senderPublicKey
                 builder.sourceDevice = 1
                 builder.content = message.toProto().toByteString()
-                builder.serverTimestamp = message.serverID ?: 0
                 builder.timestamp = message.sentTimestamp
                 val envelope = builder.build()
                 val job = MessageReceiveJob(envelope.toByteArray(), isBackgroundPoll, message.serverID, serverRoomId)