Deprecate description and externalRef in favor of metadata

[sabineschaller]

In some use cases, description and externalRef are overkill, where in others, it may not be enough. I vote for using metadata instead. Making it type string and stringify everything would probably be easiest.

[wilsonianb]

Or memos 😜
https://xrpl.org/transaction-common-fields.html#memos-field

[adrianhopebailie]

Memos seems like a nice way to have SOME structure.
Basically an array of objects with a rel, type, and value.
(Odd that memos in XRPL use format for the mime-type)

Format can default to text/plain

{
  "memos": [
    {
      "rel": "invoiceNumber",
      "value": "INV542654"
    },
    {
      "rel": "description",
      "value": "Payment for the widgets"
    },
    {
      "rel": "invoice",
      "type": "application/pdf"
      "value": "<base64encoded PDF>"
    } 
  ]
}