The id of the attachment file in the Proposales database
What type of file the attachment represents. It can be
application/pdf
for a pdf file, image/jpeg
or image/png
for an image, text/html
for a url.A short, descriptive text to be shown as the title for the attachment.
In the case of a url, the address to link to. Optional.
The uuid under which the contents of the pdf or image file are saved in the Proposales backend.