URL-encoded HTTP requests

[mihaitodor]

Here's a sample config which shows how to perform a application/x-www-form-urlencoded HTTP POST request:

input:
  generate:
    count: 1
    mapping: |
      root.foo = "bar"
      root.fizz = "buzz"
  processors:
    - mapping: |
        root = this.key_values().map_each(kv -> kv.key + "=" + kv.value).join("&")
    - http:
        url: http://localhost:6666
        verb: "POST"
        headers:
          Content-Type: "application/x-www-form-urlencoded"