Mustache templates should escape JSON, not HTML

[clintongormley]

Currently we're using the default escape method from Mustache, which is intended for escaping HTML, not JSON.

This results in things like " -> "

Instead, we should be using these escapes:

\b  Backspace (ascii code 08)
\f  Form feed (ascii code 0C)
\n  New line
\r  Carriage return
\t  Tab
\v  Vertical tab
\"  Double quote
\\  Backslash 

[clintongormley]

Test case:

DELETE /t

PUT /t
{
  "mappings": {
    "foo": {
      "properties": {
        "bar": {
          "type": "string",
          "index": "not_analyzed"
        }
      }
    }
  }
}

PUT /t/foo/1
{
  "foo": "bar&"
}

GET /_search/template
{
  "template": {
    "query": {
      "term": {
        "foo": "{{foo}}"
      }
    }
  },
  "params": {
    "foo": "bar&"
  }
}

[s1monw]

cool I will take a look at it