[WIP] Makes category a multi-select

Trying to make batches of categories selectable by label:

Made the form a multi, though that has lost the styling on optgroup labels.

As I see it, clicking on an optgroup label should select the group of categories
under it. Styling needs to be fixed for the label - and/or the label should
have its own checkbox.

perllib/FixMyStreet/App/Controller/Dashboard.pm

@@ -127,7 +127,7 @@ sub index : Path : Args(0) {
         $c->forward('/report/stash_category_groups', [ $c->stash->{contacts} ]);
 
         # See if we've had anything from the body dropdowns
-        $c->stash->{category} = $c->get_param('category');
+        $c->stash->{category} = [ $c->get_param_list('category') ];
         $c->stash->{ward} = [ $c->get_param_list('ward') ];
 
         if ($c->user_exists) {

perllib/FixMyStreet/Reporting.pm

@@ -18,7 +18,7 @@ has on_updates => ( is => 'lazy', default => sub { $_[0]->type eq 'updates' } );
 
 has body => ( is => 'ro', isa => Maybe[InstanceOf['FixMyStreet::DB::Result::Body']] );
 has wards => ( is => 'ro', isa => ArrayRef[Int], default => sub { [] } );
-has category => ( is => 'ro', isa => Maybe[Str] );
+has category => ( is => 'ro', isa => ArrayRef[Maybe[Str]], default => sub { [] } );
 has state => ( is => 'ro', isa => Maybe[Str] );
 has start_date => ( is => 'ro',
     isa => Str,
@@ -90,7 +90,7 @@ has csv_extra_data => ( is => 'rw', isa => CodeRef );
 has filename => ( is => 'rw', isa => Str, lazy => 1, default => sub {
     my $self = shift;
     my %where = (
-        category => $self->category,
+        category => join(',', @{$self->category}),
         state => $self->state,
         ward => join(',', @{$self->wards}),
         start_date => $self->start_date,

templates/web/base/dashboard/index.html

@@ -51,9 +51,9 @@ <h1>[% loc('Summary statistics') %]</h1>
 
     <p>
         <label for="category">[% loc('Category:') %]</label>
-        <select class="form-control" name="category" id="category"><option value=''>[% loc('All') %]</option>
+        <select class="form-control js-multiple" multiple name="category" id="category"><option value=''>[% loc('All') %]</option>
             [% BLOCK category_option %]
-                <option value='[% cat.category | html %]'[% ' selected' IF category == cat.category %]>[% cat.category_display | html %]</option>
+                <option value='[% cat.category | html %]'[% ' selected' IF category.grep(cat.category).size %]>[% cat.category_display | html %]</option>
             [% END %]
             [%~ INCLUDE 'report/new/_category_select.html' ~%]
         </select>