Adds OmitConnection parameter to broadcast (#20723)

* Adds OmitConnection parameter to broadcast

Currently we have no means to omit sending a websocket event to a
specific connection id.
This is needed mainly so that the initiator won't receive an event for
the action it just initiated.
Will be used for the global drafts feature, so that we won't update
drafts through ws when a user is typing.

This commit adds OmitConnection to the Broadcast struct and to the
NewWebSocketEvent function signature.
shouldSendEvent should return false for that specific connection.

* Return early only if connection id matches the omitted

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/websocket_test.go

@@ -41,7 +41,7 @@ func TestWebSocketEvent(t *testing.T) {
 
 	omitUser := make(map[string]bool, 1)
 	omitUser["somerandomid"] = true
-	evt1 := model.NewWebSocketEvent(model.WebsocketEventTyping, "", th.BasicChannel.Id, "", omitUser)
+	evt1 := model.NewWebSocketEvent(model.WebsocketEventTyping, "", th.BasicChannel.Id, "", omitUser, "")
 	evt1.Add("user_id", "somerandomid")
 	th.App.Publish(evt1)
 
@@ -69,7 +69,7 @@ func TestWebSocketEvent(t *testing.T) {
 
 	require.True(t, eventHit, "did not receive typing event")
 
-	evt2 := model.NewWebSocketEvent(model.WebsocketEventTyping, "", "somerandomid", "", nil)
+	evt2 := model.NewWebSocketEvent(model.WebsocketEventTyping, "", "somerandomid", "", nil, "")
 	th.App.Publish(evt2)
 	time.Sleep(300 * time.Millisecond)