allow to normalize ISBNs in any field

 "fullTextIndex": [
        {
          "fieldName": "keyword",
          "multiFieldNames": "title,contributors[*].name,identifiers[*].value”,
          “normalizeLeadDigits” : “yes”  
        },
        {
          "fieldName": "title"
                                  “
        },
        {
          "fieldName": "languages"
        },
        {
          "fieldName": "contributors",
          "arraySubfield" : "name",
          "arrayModifiers": ["contributorNameTypeId"]
        },
        {
          "fieldName": "identifiers",
          "arraySubfield" : "value",
          "arrayModifiers": ["identifierTypeId"] 
          “normalizeLeadDigits” : “yes”  
        }
      ]
    },


normalizeLeadDigits_index — keeps the original series of digits and additionally add a normalised token, it runs only on the first occurrence of the series of digits
             “11-22 33 yyy” -> “ 11-22 33 112233 yyy”
             “xxx 11-22 33 yyy” -> “ xxx 11-22 33 yyy”


normalizeLeadDigits_query replaces the original series of digits with a normalised token, it runs only on the first occurrence of the series of digits

            “11-22abc yyy” -> “1122 abc yyy”
            “xxx 11-22abc yyy” -> “xxx 11-22abc yyy”