Contract and Draft Contract Attachments

You can now attach files to contracts and draft contracts, list them and remove them through the API.
Attachments include files added in the Rillet application or imported from Salesforce.

• POST /contracts/{contract_id}/documents and POST /draft-contracts/{draft_contract_id}/documents
  upload one PDF, JPEG, PNG or XLSX file as multipart/form-data in the file field and return
  the new attachment.
• GET /contracts/{contract_id}/documents and GET /draft-contracts/{draft_contract_id}/documents
  list attachments, oldest first, with a download URL that is valid for up to 1 hour.
• DELETE /contracts/{contract_id}/documents/{document_id} and
  DELETE /draft-contracts/{draft_contract_id}/documents/{document_id} remove an attachment. The
  stored file is deleted unless another contract, draft contract or milestone still uses it, or it
  belongs to another part of Rillet.

A file may be at most 9 MiB. A contract or draft contract can have at most 20 attachments totalling
at most 100 MiB, counting files added in the Rillet application or imported from Salesforce. When a
draft contract is confirmed, its attachments move to the contract. Re-creating a draft contract with
POST /draft-contracts and the same external reference discards its attachments; use PUT to change it.

Applies to V4 only.