DATAMONGO-2545 - Fix regression in String query SpEL parameter binding.

[christophstrobl]

The PR includes a fix for parameter binding within a SpEL expression using query parameter placeholders ?0, ?1,... instead of the array index [0],[1],...

@Query("{ 'hidden' : ?#{ hasRole('batman') ? '?0' : '?1' } }"
List<User> findAllUsingSpelBy(String arg0, String arg1);

It also fixes the case where the SpEL expression actually results in the query document to use.

@Query("?#{ hasRole('admin') ? { 'region': 'all' } : { 'user.superviser':  principal.id } }")
List<User> findAllUsingSpelBy();

[mp911de]

That's merged, polished, and backported now.