Collective attributes from multiple sources are not combined

[fyrbach]

When collective multi-value attributes of the same type are inherited from multiple sources, only attribute values from one source are currently applied. Values from other sources are ignored.

I suspect this issue originates from the following code:

wrends/opendj-server-legacy/src/main/java/org/opends/server/types/Entry.java

Lines 3027 to 3033 in cd95048

	if (attrList.get(0).isVirtual())
	{
	// The existing attribute is already virtual,
	// so we've got a different conflict, but we'll let the first win.
	// FIXME -- Should we handle this differently?
	return;
	}

Expected behavior:

According to RFC 3671, section 1.2 ("Collective Attributes"), collective attributes inherited from multiple sources should be combined, aggregating all attribute values.

When an entry belongs to multiple entry collections, the entry's
values of each collective attribute are combined such that
independent sources of these values are not manifested to clients.

Affected version:

Wren:DS 5.0.1