The current behavior of the MapViewer template when displaying the list of available basemaps is:
User not signed in: pick up ArcGIS Online default basemaps.
User signed in: picks up the basemap gallery set for the org the user is signed in to.
In our use case, we would like to define exactly which basemaps the users can choose from, so we can choose ones that are most relevant to our application and thereby simplify the experience.
Ideally, a template configuration property would allow setting the id of a custom group that the template would use to pull the list of basemaps from.
