====== util.encodings API ======
Provides an interface for translating a string into various common encodings.

Currently provided are: base64, idna, stringprep.

===== Usage =====
<code lua>
   local encodings = require "util.encodings";

   print(encodings.base64.encode("Hello world!")) -- prints "SGVsbG8gd29ybGQh"

   -- or individually --
   local base64 = require "util.encodings".base64;
   local idna = require "util.encodings".idna;
   local stringprep = require "util.encodings".stringprep;

</code>

===== Reference =====

==== base64 ====

 === encode(string) ===
  Returns a base64-encoded equivalent of a string.

 === decode(string) ===
  Returns a decoded equivalent of a base64 string, or nil if the string is invalid base64.

==== idna ====
IDNA provides a way to safely convert unicode domain names to an ASCII equivalent, and back again.
 === to_ascii(string) ===
  Returns an ASCII-safe version of a unicode domain name, or nil for an invalid domain.

 Example:
 <code lua>
   print(encodings.idna.to_ascii("➡.ws"))
 </code>
 <code>
   xn--hgi.ws
 </code>

 === to_unicode(string) ===
  Returns the original unicode version of an ASCII IDNA-encoded domain.

 Example:
 <code lua>
   print(encodings.idna.to_ascii("➡.ws"))
 </code>
 <code>
   ➡.ws
 </code>

==== stringprep ====
Stringprep defines a way of processing and normalizing strings according to a set of rules (a profile). Prosody implements 4profiles:

  * nodeprep (for usernames, the node part of a JID)
  * resourceprep (for resources and MUC nicknames)
  * saslprep (for applying to strings prior to calculating SASL challenges)
  * nameprep (for applying to hostnames/domains)

 Example:
 <code lua>
   print(encodings.stringprep.nodeprep("HelloWorld"))
 </code>
 <code>
  helloworld
 </code>

All stringprep functions return nil when the input is not a valid string in that particular profile.