Bug 1984139: Resume add composite to have a validate function

For point 2

- The validation was being done as part of the submission after the
item was created.

We need to have a validation function to do the file attachment check
before the submission so we don't create a record.

Change-Id: I01ab672a677e4c0670f7e85debf68bb6822283e4
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>