MM-48246 - AB test open RHS with linked board (#22201)

* MM-48246 - AB test open RHS with linked board

* fix linter

* fix go vet complain

* implement pr feedback

* fix mispelling

* remove unnecesary comment

* add pr feedback

* fix translation texts

* fallback for the first system stored value

* implement PR feedback

* prevent calling property from potential null object

* use the default hash id for welcome to boards template

model/preference.go

@@ -33,6 +33,9 @@ const (
 	PreferenceRecommendedNextSteps        = "recommended_next_steps"
 	PreferenceNameInsights                = "insights_tutorial_state"
 
+	// initial onboarding preferences
+	PreferenceOnboarding = "onboarding"
+
 	PreferenceCategoryTheme = "theme"
 	// the name for theme props is the team id