Validate file using UUID

[vitormattos]

All files have a file UUID. This UUID must be printed on the PDF so that it can be used on the document validation site.

Backend

• Implement endpoint in the API to validate a UUID
  • /apps/libresign/api/0.1/file/validate/<uuid>
• Print the UUID of the file in the PDF.
• Check if there is a need to return data contained in the signed PDF in addition to the metadata saved in the system.
  Estimate: 2h

Frontend

• Request the UUID field on the validation form
• Make a request to the endpoint that returns the data of a UUID
• Display the data on the screen.
• Show link to download or view the PDF file. I don't know what the best option is
  Estimate: 2h