Support index settings defination

`ElasticquentTrait@createIndex` now creating with custom index settings
and mappings if exists.

Author: chuangbo

readme.md

@@ -138,6 +138,55 @@ If you want a simple way to create indexes, Elasticquent models have a function
 
     Book::createIndex($shards = null, $replicas = null);
 
+For custom analyzer, you can set an `indexSettings` property in your model and define the analyzers from there:
+
+```php
+    /**
+     * The elasticsearch settings.
+     *
+     * @var array
+     */
+    protected $indexSettings = [
+        'analysis' => [
+            'char_filter' => [
+                'replace' => [
+                    'type' => 'mapping',
+                    'mappings' => [
+                        '&=> and '
+                    ],
+                ],
+            ],
+            'filter' => [
+                'word_delimiter' => [
+                    'type' => 'word_delimiter',
+                    'split_on_numerics' => false,
+                    'split_on_case_change' => true,
+                    'generate_word_parts' => true,
+                    'generate_number_parts' => true,
+                    'catenate_all' => true,
+                    'preserve_original' => true,
+                    'catenate_numbers' => true,
+                ]
+            ],
+            'analyzer' => [
+                'default' => [
+                    'type' => 'custom',
+                    'char_filter' => [
+                        'html_strip',
+                        'replace',
+                    ],
+                    'tokenizer' => 'whitespace',
+                    'filter' => [
+                        'lowercase',
+                        'word_delimiter',
+                    ],
+                ],
+            ],
+        ],
+    ];
+
+```
+
 For mapping, you can set a `mappingProperties` property in your model and use some mapping functions from there:
 
 ```php

src/ElasticquentTrait.php

@@ -137,6 +137,16 @@ public function setMappingProperties(array $mapping = null)
         $this->mappingProperties = $mapping;
     }
 
+    /**
+     * Get Index Settings
+     *
+     * @return array
+     */
+    public function getIndexSettings()
+    {
+        return $this->indexSettings;
+    }
+
     /**
      * Is Elasticsearch Document
      *
@@ -527,6 +537,11 @@ public static function createIndex($shards = null, $replicas = null)
             'index' => $instance->getIndexName(),
         );
 
+        $settings = $instance->getIndexSettings();
+        if (!is_null($settings)) {
+            $index['body']['settings'] = $settings;
+        }
+
         if (!is_null($shards)) {
             $index['body']['settings']['number_of_shards'] = $shards;
         }
@@ -535,6 +550,14 @@ public static function createIndex($shards = null, $replicas = null)
             $index['body']['settings']['number_of_replicas'] = $replicas;
         }
 
+        $mappingProperties = $instance->getMappingProperties();
+        if (!is_null($mappingProperties)) {
+            $index['body']['mappings'][$instance->getTypeName()] = [
+                '_source' => array('enabled' => true),
+                'properties' => $mappingProperties,
+            ];
+        }
+
         return $client->indices()->create($index);
     }