proof of concept English synonym stemmer for ElasticSearch

References:
https://qbox.io/blog/tutorial-search-plurals-analyzers-elasticsearch
https://www.elastic.co/guide/en/elasticsearch/reference/current/search-analyzer.html
https://www.elastic.co/guide/en/elasticsearch/reference/6.2/analysis-lang-analyzer.html
https://stackoverflow.com/questions/24257747/normalize-british-and-american-english-for-elasticsearch
https://www.elastic.co/guide/en/elasticsearch/reference/6.1/analysis-mapping-charfilter.html 
https://www.elastic.co/guide/en/elasticsearch/reference/current/analysis-synonym-tokenfilter.html 

curl -X PUT "localhost:9200/recipes" -H 'Content-Type: application/json' -d'
{
  "settings": {
    "analysis": {
        "char_filter": {
            "en_char_filter": { "type": "mapping", "mappings": ["aerie=>axerie", "aeroplane=>airplane", "aloe=>aloxe", "canoe=>canoxe", "coerce=>coxerce", "poem=>poxem", "prise=>prixse","armour=>armor", "behaviour=>behavior", "centre=>center", "colour=>color", "clamour=>clamor", "draught=>draft", "endeavour=>endeavor", "favour=>favor", "flavour=>flavor", "harbour=>harbor", "honour=>honor","humour=>humor", "labour=>labor", "litre=>liter", "metre=>meter", "mould=>mold", "neighbour=>neighbor", "plough=>plow", "saviour=>savior", "savour=>savor","ae=>e", "ction=>xion", "disc=>disk", "gramme=>gram", "isable=>izable", "isation=>ization", "ise=>ize", "ising=>izing", "ll=>l", "oe=>e", "ogue=>og", "sation=>zation", "yse=>yze", "ysing=>yzing"] }
        },
        "filter": {
            "english_stop": {
              "type":       "stop",
              "stopwords":  "_english_" 
            },
            "english_keywords": {
              "type":       "keyword_marker",
              "keywords":   ["example"] 
            },
            "english_stemmer": {
              "type":       "stemmer",
              "language":   "english"
            },
            "english_possessive_stemmer": {
              "type":       "stemmer",
              "language":   "possessive_english"
            },
            "english_synonym_stemmer": {
                "type": "synonym",
                "synonyms": ["grey=>gray", "greyness=>grayness"]
            }
          },
        "analyzer": {
            "english": {
              "tokenizer":  "standard",
              "char_filter": ["en_char_filter"],
              "filter": [
                "english_possessive_stemmer",
                "lowercase",
                "english_stop",
                "english_keywords",
                "english_stemmer",
                "english_synonym_stemmer"
              ]
            }
          }
    }
  },
  "mappings": {
    "recipe": {
      "properties": {
        "title": {
          "type": "text",
          "analyzer": "english",
          "search_analyzer": "english"
        },
        "ingredients": {
          "type": "text",
          "analyzer": "english",
          "search_analyzer": "english"
        },
        "categories": {
          "type": "text",
          "analyzer": "english",
          "search_analyzer": "english"
        },
        "description": {
          "type": "text",
          "analyzer": "english",
          "search_analyzer": "english"
        }
      }
    }
  }
}'
curl -XPUT 'localhost:9200/recipes/recipe/1?pretty' -d '{ 
       "title" :"Fresh Orange Pie",
        "ingredients" : "pastry dough,   navel orange, sugar, vanilla, coconut",
        "description" : "Meanwhile, peel orange and section into segments...",
        "categories" : ["pie", "orange"] 
  }' -H 'Content-Type: application/json' 
curl -XPUT 'localhost:9200/recipes/recipe/2?pretty' -d '{ 
         "title" :"Perfect Apple Pie",
         "ingredients" : "refrigerated pie crusts,  apple, sugar, all-purpose flour, cinnamon, salt, lemon juice",
          "description" : "Heat oven to 425°F. Place 1 pie crust in ungreased 9-inch glass pie plate. Press firmly against side and bottom...",
        "categories" : ["pie", "apple"]
    }' -H 'Content-Type: application/json' 
curl -XPUT 'localhost:9200/recipes/recipe/3?pretty' -d '{
        "title" : "Apples Jam",
         "ingredients" : "apples, sugar, vanilla",
          "description" : "Bring sugar and 3 Tbsp. water to a boil in a large pot over medium-high heat, stirring to dissolve sugar….",
        "categories" : ["jam", "apples"]
    }' -H 'Content-Type: application/json' 
curl -XPUT 'localhost:9200/recipes/recipe/3?pretty' -d '{
        "title" : "Apples Jam",
         "ingredients" : "apples, sugar, vanilla",
          "description" : "Bring sugar grey and 3 Tbsp. water to a boil in a large pot over medium-high heat, stirring to dissolve sugar….",
        "categories" : ["jam", "apples"]
    }' -H 'Content-Type: application/json' 

curl -XGET 'localhost:9200/recipes/_search?q=oranges'
curl -XGET 'localhost:9200/recipes/_search?q=gray'