[O] non-standard link errors

[Skip Collins]

Org throws an error when I export html with a link type that it does
not know about. I would like it to simply add the link to the exported
document without checking its validity. For example, I have a link
that, when tapped on an iPhone, will open a particular app. I would
like the html to look something like:
<a href="facetime:address@hidden">Connect using FaceTime</a>

The link works on an iPhone. But Org won't generate the html. Other
apps uses x-callback-url links formatted like this:
x-appname://x-callback-url/import?&description=Open%20Mail.app.....

These also do not work. Short of adding every type I might want to use
with org-add-link-type, is it possible to disable the export error and
just pass links through as written?