Added the API definition for `_explain`

rest-api-spec/api/explain.json

@@ -7,42 +7,81 @@
       "paths": ["/{index}/{type}/{id}/_explain"],
       "parts": {
         "id": {
+          "type" : "string",
+          "required" : true,
+          "description" : "The document ID"
         },
         "index": {
+          "type" : "string",
+          "required" : true,
+          "description" : "The name of the index"
         },
         "type": {
+          "type" : "string",
+          "required" : true,
+          "description" : "The type of the document"
         }
       },
       "params": {
         "analyze_wildcard": {
+          "type" : "boolean",
+          "description" : "Specify whether wildcards and prefix queries in the query string query should be analyzed (default: false)"
         },
         "analyzer": {
+          "type" : "string",
+          "description" : "The analyzer for the query string query"
         },
         "default_operator": {
+          "type" : "enum",
+          "options" : ["AND","OR"],
+          "default" : "OR",
+          "description" : "The default operator for query string query (AND or OR)"
         },
         "df": {
+          "type" : "string",
+          "description" : "The default field for query string query (default: _all)"
         },
         "fields": {
+          "type": "list",
+          "description" : "A comma-separated list of fields to return in the response"
         },
         "id": {
+          "type" : "string",
+          "description" : "The document ID"
         },
         "lenient": {
+          "type" : "boolean",
+          "description" : "Specify whether format-based query failures (such as providing text to a numeric field) should be ignored"
         },
         "lowercase_expanded_terms": {
+          "type" : "boolean",
+          "description" : "Specify whether query terms should be lowercased"
         },
         "parent": {
+          "type" : "string",
+          "description" : "The ID of the parent document"
         },
         "preference": {
+          "type" : "string",
+          "description" : "Specify the shards the operation should be performed on (default: random shard)"
         },
         "q": {
+          "type" : "string",
+          "description" : "Query in the Lucene query string syntax"
         },
         "routing": {
+          "type" : "string",
+          "description" : "Specific routing value"
         },
         "source": {
+          "type" : "string",
+          "description" : "The URL-encoded query definition (instead of using the request body)"
         }
       }
     },
     "body": {
+      "required" : true,
+      "description" : "The query definition using the Query DSL"
     }
   }
 }