Bug 33490: Improve max date handling

Bug 33490: Improve max date handling

It fixes:
1. /agreements?by_expired=true do no longer explode
2. Fill date with today's date when we setup the component and when we
hit "filter"

However there are a couple of things totally wrong:
1. We should not need is_fp_disabled, we could be able to use
  :disabled="!filters.by_expired"
in the template, but it does not work
2. We should not need to deal with filters.max_expiration_date the "old
JS way", but should use a Vue computed value instead. I've failed at
that

I think those 2 problems have the same root, the way we deal with
filters in data() is wrong, and we may be loosing the ref at some point.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>