Add Adapter to Translate Jwt to BearerTokenAuthentication

[jzheaux]

JwtAuthenticationProvider by default produces a JwtAuthenticationToken by default upon successful authentication.

In order to assist with using jwt(), but also the more generic authentication result BearerTokenAuthentication, an adapter would be handy.

This can be realized in the form of a Converter<Jwt, AbstractAuthenticationToken> which can then be installed via

http
    .oauth2ResourceServer()
        .jwt()
            .jwtAuthenticationConverter(new JwtBearerTokenAuthenticationConverter())