Attachments for Manual Journal Entries

Two new endpoints support attachments on existing manual journal entries:

• POST /journal-entries/{journal_entry_id}/documents uploads one PDF, JPEG, or PNG of up to 20 MiB
  as multipart form data and returns 204. Existing attachments are preserved; repeating an upload
  creates another attachment.
• GET /journal-entries/{journal_entry_id}/documents lists attachment IDs, filenames, and download
  URLs, including files uploaded through the Rillet application. URLs are valid for up to 1 hour;
  call the endpoint again to obtain fresh URLs.

Create the journal entry before uploading attachments. System-generated and non-posting entries
are not supported.

Applies to V4 only.