Prep for MS Teams plugin API (#25565)

* - columns added to ShareChannelRemotes: lastpostcreateat, lastpostupdateat
- SyncMsg and SyncResponse moved to `model` package
- field added to RemoteCluster struct: PluginID

* sync new posts before updated posts to ensure post order in MS Teams

* add plugid to remoteclusters table and store

* don't sync history by default

server/platform/services/sharedchannel/channelinvite.go

@@ -87,6 +87,8 @@ func (scs *Service) SendChannelInvite(channel *model.Channel, userId string, rc
 			RemoteId:          rc.RemoteId,
 			IsInviteAccepted:  true,
 			IsInviteConfirmed: true,
+			LastPostCreateAt:  model.GetMillis(),
+			LastPostUpdateAt:  model.GetMillis(),
 		}
 		if _, err = scs.server.GetStore().SharedChannel().SaveRemote(scr); err != nil {
 			scs.sendEphemeralPost(channel.Id, userId, fmt.Sprintf("Error confirming channel invite for %s: %v", rc.DisplayName, err))
@@ -169,6 +171,8 @@ func (scs *Service) onReceiveChannelInvite(msg model.RemoteClusterMsg, rc *model
 		IsInviteAccepted:  true,
 		IsInviteConfirmed: true,
 		RemoteId:          rc.RemoteId,
+		LastPostCreateAt:  model.GetMillis(),
+		LastPostUpdateAt:  model.GetMillis(),
 	}
 
 	if _, err := scs.server.GetStore().SharedChannel().SaveRemote(sharedChannelRemote); err != nil {