Bug 28316: escape brackets in the search query

This patch screens square and curly brackets which have no special
language meaning.

To reproduce:
1) using ES, search for the book with title that contains
square and/or curly brackets, like "book [second edition]", which will
result in error.
2) apply the patch.
3) search for that book again, ensure that it works now.

Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Alex Buckley <alexbuckley@catalyst.net.nz>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

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

Koha/SearchEngine/Elasticsearch/QueryBuilder.pm

@@ -930,7 +930,6 @@ sub _clean_search_term {
     $term =~ s/=/:/g;
 
     $term = $self->_convert_index_strings_freeform($term);
-    $term =~ s/[{}]/"/g;
 
     # Remove unbalanced quotes
     my $unquoted = $term;
@@ -952,6 +951,8 @@ sub _clean_search_term {
     # and correctly ignore unevenly backslashed:
     $term =~ s/((?<!\\)(?:[\\]{2})*:[^:\s]+(?<!\\)(?:[\\]{2})*)(?=:)/$1\\/g;
 
+    # screen all brackets with backslash
+    $term =~ s/(?<!\\)(?:[\\]{2})*([\{\}\[\]])$lookahead/\\$1/g;
     return $term;
 }