Work around authentication check blocking-call bug in Quarkus 1.10.x.

A bug causes authentication checks to fail when performed from inside
a reactive operation:

    https://github.com/quarkusio/quarkus/issues/13835

To avoid such a reactive operation, we now render the HTML template
eagerly even in NewsletterResource#register, which is otherwise a
reactive implementation.

Change-Id: I26d6c1cc76eaa041a04c106b7cf06f024a0cded3
1 file changed