added the custom icon and username for the outgoing webhook and its response (#9141)

* 8272 added the username and icon as part of the model and persisted the same

* 8272 added the custome icon and name when set to the web hook response

* 8272 changed the infinte loop to timeout after 5 seconds

* 8272  fixed review comments

model/outgoing_webhook_test.go

@@ -121,6 +121,26 @@ func TestOutgoingWebhookIsValid(t *testing.T) {
 	if err := o.IsValid(); err != nil {
 		t.Fatal(err)
 	}
+
+	o.Username = strings.Repeat("1", 65)
+	if err := o.IsValid(); err == nil {
+		t.Fatal("should be invalid")
+	}
+
+	o.Username = strings.Repeat("1", 64)
+	if err := o.IsValid(); err != nil {
+		t.Fatal("should be invalid")
+	}
+
+	o.IconURL = strings.Repeat("1", 1025)
+	if err := o.IsValid(); err == nil {
+		t.Fatal(err)
+	}
+
+	o.IconURL = strings.Repeat("1", 1024)
+	if err := o.IsValid(); err != nil {
+		t.Fatal(err)
+	}
 }
 
 func TestOutgoingWebhookPayloadToFormValues(t *testing.T) {