[#1383] bugfix: fix exception mapper type from registered features

[lprimak]

Changed registration of UnauthenticatedException.class to UnauthenticatedExceptionMapper.class Jax-rs feature context.
fixes #1383

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[zenios]

LGTM

[fpapon]

@lprimak good catch!

[lprimak]

Credit where credit is due, @zenios discovered this.

[fpapon]

@zenios good catch and thank you for your contribution!

[bmarwell]

Wow, how was this not discovered before? 😁