Bug 19234: Add query parameters handling helpers

This patch introduces a Mojolicious plugin to be used on the REST api.
It adds a helper method:

generate_dbic_query
===================

When used, it generates what's needed to perform a search on
DBIC/Koha::Objects like this:

    my $params  = $c->validation->output;
    my ($filtered_params, $reserved_params) = $c->extract_reserved_params($params);

    my $filter = do_smth($filtered_params, $reserved_params);
    my $attributes = do_smth_reserved($reserved_params);

    my $patrons = Koha::Patrons->search( $filter, $attributes );

It introduces reserved param names:
- _match
- _order_by
- _page
- _per_page

They are reserved for later usage (pagination, matching algorithm on building DB queries)

All the plugin's behaviour is tested.

To test:
- Run:
  $ sudo koha-shell kohadev
 k$ cd kohaclone
 k$ prove t/Koha/REST/Plugin/Query.t
=> SUCCESS: Tests pass!
- Sign off :-D

Sponsored-by: ByWater solutions
Sponsored-by: Camden County

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>

Signed-off-by: Lari Taskula <lari.taskula@jns.fi>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Koha/REST/Plugin/Query.pm

@@ -0,0 +1,84 @@
+package Koha::REST::Plugin::Query;
+
+# This file is part of Koha.
+#
+# Koha is free software; you can redistribute it and/or modify it under the
+# terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 3 of the License, or (at your option) any later
+# version.
+#
+# Koha is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with Koha; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+use Modern::Perl;
+
+use Mojo::Base 'Mojolicious::Plugin';
+
+=head1 NAME
+
+Koha::REST::Plugin::Query
+
+=head1 API
+
+=head2 Mojolicious::Plugin methods
+
+=head3 register
+
+=cut
+
+sub register {
+    my ( $self, $app ) = @_;
+
+=head2 Helper methods
+
+=head3 extract_reserved_params
+
+    my ( $filtered_params, $reserved_params ) = $c->extract_reserved_params($params);
+
+Generates the DBIC query from the query parameters.
+
+=cut
+
+    $app->helper(
+        'extract_reserved_params' => sub {
+            my ( $c, $params ) = @_;
+
+            my $reserved_params;
+            my $filtered_params;
+
+            my $reserved_words = _reserved_words();
+
+            foreach my $param ( keys %{$params} ) {
+                if ( grep { $param eq $_ } @{$reserved_words} ) {
+                    $reserved_params->{$param} = $params->{$param};
+                }
+                else {
+                    $filtered_params->{$param} = $params->{$param};
+                }
+            }
+
+            return ( $filtered_params, $reserved_params );
+        }
+    );
+}
+
+=head2 Internal methods
+
+=head3 _reserved_words
+
+    my $reserved_words = _reserved_words();
+
+=cut
+
+sub _reserved_words {
+
+    my @reserved_words = qw( _match _order_by _page _per_page );
+    return \@reserved_words;
+}
+
+1;