||A wrapper around ImmutableList builder that produces immutable lists if elements are added to the
builder or a collapsed list otherwise.
||Attempting to access a property of a collapsed object should throw an exception, indicating that it was not in the
||A map with the RestEnrichable annotation, indicating that this map should be converted to a RestEntity
and enriched by the REST stack.
||An expanded reference has a value, call get() will return that referent value.
||A Map builder for
||A reference to a model object.