api/v0: simplify Tags model get

Since previous commit, get only effectively serves search for ids or
displays. Remove the machinery to deal with other stuff and simplify
error checking.

lib/Pooru/API/V0/Model/Tags.pm

@@ -1,6 +1,8 @@
 package Pooru::API::V0::Model::Tags;
 use v5.40;
 
+use Carp;
+
 use Pooru::API::V0::Model::PagedResults;
 
 
@@ -29,26 +31,18 @@ sub random_id ($self)
 
 sub get ($self, %search)
 {
-	my $key = exists($search{id}) ?
+	croak "Exactly one of 'id' or 'display' must be defined" if
-	    "id" : exists($search{display}) ?
+	    !(defined($search{id}) ^^ defined($search{display}));
-	    "display" : "name";
-	my $where_clause = where_in($key, $search{$key}->@*);
-	my @bind_values = $search{$key}->@*;
 
-	if (exists($search{kind_id})) {
+	my $key = defined($search{id}) ? "id" : "display";
-		$where_clause .= " AND kind_id = ?";
+	my $where_clause = where_in($key, $search{$key}->@*);
-		push(@bind_values, $search{kind_id});
-	}
 
 	my $sth = $self->{_dbh}->prepare(qq{
-	SELECT *
+		SELECT * FROM tag WHERE $where_clause LIMIT ?
-	FROM tag
-	WHERE $where_clause
-	LIMIT ?
 	});
 
 	return Pooru::API::V0::Model::Results->new($sth, $slice,
-	    (@bind_values, $self->ROWS));
+	    ($search{$key}->@*, $self->ROWS));
 }
 
 sub _ranked ($self, $stmt, @bind_values)