MM-31063: Change constants to use CamelCase (#16608)

* MM-31063: Change constants to use CamelCase

* store package

* change allcaps to camel case (#16615)

* New tools.mod

Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

app/command.go

@@ -394,7 +394,7 @@ func (a *App) tryExecuteCustomCommand(args *model.CommandArgs, trigger string, m
 		var nfErr *store.ErrNotFound
 		switch {
 		case errors.As(ur.NErr, &nfErr):
-			return nil, nil, model.NewAppError("tryExecuteCustomCommand", MISSING_ACCOUNT_ERROR, nil, nfErr.Error(), http.StatusNotFound)
+			return nil, nil, model.NewAppError("tryExecuteCustomCommand", MissingAccountError, nil, nfErr.Error(), http.StatusNotFound)
 		default:
 			return nil, nil, model.NewAppError("tryExecuteCustomCommand", "app.user.get.app_error", nil, ur.NErr.Error(), http.StatusInternalServerError)
 		}