[FIX] account: use proforma preview for non-printed invoices

Issue
-----

If an invoice is created, but not yet "Send & Print", the portal preview shows a normal invoice,
but when "Download"ed from the portal preview, a proforma invoice is downloaded. The download
behavior is intended since the client shouldn't be able to get a "final" invoice themselves,
before the accountant generates one with "Send & Print". However, the HTML preview should also
show a proforma invoice to be consistent with this, so the user downloads what they see.

Steps
-----

 - Create a new invoice: Accounting -> Customers -> Invoices -> New -> ...
 - Go to portal by clicking on "Preview".
 - You'll see a normal invoice. Now click "Download".
 - A proforma invoice is downloaded.

Cause
-----

The HTML-rendered invoice in the portal preview isn't configured to be proforma.

opw-3848049

closes odoo/odoo#161726

Signed-off-by: Claire Bretton (clbr) <clbr@odoo.com>

addons/account/controllers/portal.py

@@ -143,6 +143,8 @@ class PortalAccount(CustomerPortal):
             return request.make_response(attachments.raw, list(headers.items()))
 
         elif report_type in ('html', 'pdf', 'text'):
+            has_generated_invoice = bool(invoice_sudo.invoice_pdf_report_id)
+            request.update_context(proforma_invoice=not has_generated_invoice)
             return self._show_report(model=invoice_sudo, report_type=report_type, report_ref='account.account_invoices', download=download)
 
         values = self._invoice_get_page_view_values(invoice_sudo, access_token, **kw)

addons/account/models/ir_actions_report.py

@@ -75,3 +75,9 @@ class IrActionsReport(models.Model):
             master_report = self.env.ref(f"account.{master_xmlid}", raise_if_not_found=False)
             if master_report and master_report in self:
                 raise UserError(_("You cannot delete this report (%s), it is used by the accounting PDF generation engine.", master_report.name))
+
+    def _get_rendering_context(self, report, docids, data):
+        data = super()._get_rendering_context(report, docids, data)
+        if self.env.context.get('proforma_invoice'):
+            data['proforma'] = True
+        return data