&Check_Userid

=head2 Check_Userid

    my $uniqueness = Check_Userid($userid,$borrowernumber);

    $borrowernumber is optional (i.e. it can contain a blank value). If $userid is passed with a blank $borrowernumber variable, the database will be checked for all instances of that userid (i.e. userid=? AND borrowernumber != '').

    If $borrowernumber is provided, the database will be checked for every instance of that userid coupled with a different borrower(number) than the one provided.

    return :

        0 for not unique (i.e. this $userid already exists)

        1 for unique (i.e. this $userid does not exist, or this $userid/$borrowernumber combination already exists)

=cut

sub Check_Userid {

    my ( $uid, $borrowernumber ) = @_;

    return 0 unless ($uid); # userid is a unique column, we should assume NULL is not unique

    return 0 if ( $uid eq C4::Context->config('user') );

    my $rs = Koha::Database->new()->schema()->resultset('Borrower');

    my $params;

    $params->{userid} = $uid;

    $params->{borrowernumber} = { '!=' => $borrowernumber } if ($borrowernumber);

    my $count = $rs->count( $params );

    return $count ? 0 : 1;

}

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