Add support for the CLI to push a lambda to monitor SQS queues.

[ph]

This all support to configure triggers in the configuration file to
allow a lambda function to monitor one or more queue.

Note: we assume that body of an SQS message is a string, it we receive
a json encoded string we can use the decode_json_fields.

[urso]

This is kind of a constant. Let's move the init out of this function and introduce a global:

var reNormalizeNames = regexp.MustCompile("[:/-]")

It is not nice to have var as global constant, but this patterns catches errors/panics whenever the beat is started, not only when the regex is compiled by taking said code path.

A little trick (lisp-style) if ouy want to hide the regex (still creates a function pointer, though):

var normalizeSQSName = func() func(string) string {
  re := regex.MustCompile()
  return func(c string) string {
    return re.ReplaceAllString(c, "")
  }
}()

[urso]

As we remove these bytes, solution without regex:

func removeChars(s string, chars string) string {
  buf := &strings.Builder{}
  for len(s) > 0 {
    idx := strings.IndexAny(s, chars)
    if idx < 0 {
      if buf.Len() > 0 {
        buf.WriteString(s)
      }
      break
    }

    buf.WriteString(s[:idx])
    s = s[idx+1:]
  }

  if buf.Len() == 0 {
    return s
  }
  return buf.String()
}

Why is this missing from stdlib :/

[ph]

I have added the above method in common/string.go and tests for it.

[ph]

Updated with the reviews, added support for enabled: false in the 'yml'

[ph]

@urso rebased, it will probably conflict with another PR I have open so lets try to get it merged soonish.

[urso]

LGTM. CI failure is unrelated.

[urso]

LGTM. CI failure is unrelated.

[ph]

I've rebased this PR on top of the feature branch as soon as everything is green I will merge it.