Upload a file to the web site, to be used by a later API call or made available to the end-user
POST https://www.prayerletters.com/api/v1/files
Files that are uploaded to the web site but not attached to an order will be available to the end-user during the order process.

Successful Response

HTTP/1.1 201 Created
{ "filename" : "newsletter.pdf", "id" : "f-13g-wt17" }

Error Responses

400 invalid_filename
The filename may contain no more than 100 characters.
400 missing_filename
A filename is required.
400 no-content
The request body didn't contain any content.
400 too-large
The request body was too large.
400 unlinked_token
This API call is only available for tokens that are linked to an account.
403 missing_scope
In order to upload files, you need the orders.write scope.