[FIX] SDK: api.json transformer - annotation external links marked
[FIX] SDK: api.json transformer - annotation external links marked

The problem:
API Reference annotations are marked with external link to OData v4
which is not marked as external in the DemoKit

The root cause:
As this linked is added by the transformer script but it's not handled
by the default link transformation the link remains unmarked

The solution:
Generate the link with the handleExternalUrl method which properly
marks it as external

Note:
This is a sync for API Reference preview from Gerrit change: 3831840

Change-Id: I9e16e0da69c9f4e97cbb5d38b016b716c0f81f44
BCP: 1870551767

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5