Add support to prompt for letter parameters during invoicing

Description

Currently, documents associated with an invoice items' product are linked to the invoice item when the item is saved.
This prevents letter documents being generated, as parameters cannot be prompted for.
When a document is selected that has a letter template with parameters, support needs to be added to pop up a dialog to prompt for the parameters.
If there is more than one letter with parameters, multiple dialogs will need to be displayed, one after the other.

Environment

None

Status

Assignee

Tim Anderson

Reporter

Tim Anderson

Labels

None

Time tracking

8h

Components

Fix versions

Affects versions

Priority

Major
Configure