This is only implemented in Hiveminder::PullEncoder; in RT::PullEncoder it's resolve_user_id_to. What's this for, actually?
To install App::SD, copy and paste the appropriate command in to your terminal.
cpanm
cpanm App::SD
CPAN shell
perl -MCPAN -e shell install App::SD
For more information on module installation, please visit the detailed CPAN module installation guide.