When the validation of a field fails in a form, we disable the Done
button. With child forms, however, it did not work because they have
their own set of hidden buttons ; that are not the ones the users
interacts with.
This patch makes parent forms recurse on the child forms when checking
if any field is in error. Also, when a child form undertakes validation,
it now propagates to the parent, so that the done button can be
immediately enabled/disabled.
Having a validation error in a child form that is not currently enabled
should not prevent the user from moving forward, so we disable recursion
for child forms that are disabled.
Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>