title: What data type should I use for IETF language codes?
body: <p>I'm designing a schema for a message on a microblogging platform, which will need to have a defined language. These messages will be distributed across networks between many nodes, so I need to make the schema compact but still completely multilingual.</p>
  <p>I'm going to use the <a href="https://en.wikipedia.org/wiki/IETF_language_tag" rel="nofollow noreferrer">IETF language codes</a> (<code>en</code>, <code>en-AU</code> etc.), but I need to know if there is a specific way to represent them for the purposes of efficiency. There are multiple standards for language tags, but the current specification <a href="https://www.rfc-editor.org/rfc/rfc5646" rel="nofollow noreferrer">RFC 5646</a> is convoluted by maintaining backwards-compatibility with the previous standards. I don't exactly understand the space requirements as there are multiple subtags.</p>
  <p>What is the most space-efficient way to represent an IETF language code?</p>