Set accepted files for letter upload

app/main/views/uploads.py

@@ -292,6 +292,7 @@ def uploaded_letter_preview(service_id, file_id):
     form = LetterUploadPostageForm(
         postage_zone=postal_address.postage
     )
+    allowed_spreadsheet_file_extensions = ','.join([f'.{ext}' for ext in Spreadsheet.ALLOWED_FILE_EXTENSIONS])
 
     template = get_template(
         template_dict,
@@ -313,6 +314,7 @@ def uploaded_letter_preview(service_id, file_id):
         message=error_message,
         error_code=error_shortcode,
         form=form,
+        allowed_spreadsheet_file_extensions=allowed_spreadsheet_file_extensions,
         postal_address=postal_address,
         re_upload_form=re_upload_form
     )

app/templates/views/uploads/choose-file.html

@@ -29,6 +29,7 @@
   <p class="govuk-body">
     {{ file_upload(
       form.file,
+      allowed_file_extensions='.pdf',
       action=url_for('main.upload_letter', service_id=current_service.id),
       button_text='Upload your file again' if error else 'Choose file',
       show_errors=False

app/templates/views/uploads/preview.html

@@ -19,6 +19,7 @@
         <div class="form-group">
           {{ file_upload(
             re_upload_form.file,
+            allowed_file_extensions='.pdf',
             action=url_for('main.upload_letter', service_id=current_service.id),
             button_text='Upload your file again'
           ) }}