Refactor thesaurus query build

- Look for text nodes and infer the concepts behind term using thesaurus
- Use value objects for thesaurus terms and concepts
- Pass a QueryContext holding allowed fields and locales informations when building the Elasticsearch query
- Change type hinting and name of query building method on nodes
- Remove unused method Node#isFullTextOnly()
- Move getFieldsStructure from RecordIndexer to RecordHelper for reusing field structure in SearchEngine

lib/Alchemy/Phrasea/SearchEngine/Elastic/Search/QueryContext.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace Alchemy\Phrasea\SearchEngine\Elastic\Search;
+
+class QueryContext
+{
+    private $fields;
+    private $locales;
+    private $queryLocale;
+
+    public function __construct(array $fields, array $locales, $queryLocale)
+    {
+        $this->fields = $fields;
+        $this->locales = $locales;
+        $this->queryLocale = $queryLocale;
+    }
+
+    public function narrowToFields(array $fields)
+    {
+        // Ensure we are not escaping from original fields restrictions
+        $fields = array_intersect($this->fields, $fields);
+
+        return new static($fields, $this->locales, $this->queryLocale);
+    }
+
+    public function getLocalizedFields()
+    {
+        $fields = array();
+        foreach ($this->fields as $field) {
+            foreach ($this->locales as $locale) {
+                $boost = ($locale === $this->queryLocale) ? '^5' : '';
+                $fields[] = sprintf('caption.%s.%s%s', $field, $locale, $boost);
+            }
+            // TODO Put generic analyzers on main field instead of "light" sub-field
+            $fields[] = sprintf('caption.%s.%s', $field, 'light^10');
+        }
+
+        return $fields;
+    }
+}