Split from ``pos_payment_method_cashdro_fix`` on purpose: that module is a
temporary patch for three migration leftovers, meant to disappear as soon as
its ``upstream/*.patch`` is merged in ``OCA/pos``. This one has a longer life —
only the ``pos_session`` fix is a migration leftover, the rest are problems the
module has carried since 17.0 — so it should not go away with it.

It supersedes the ``_cashdro_url()`` patch of ``pos_payment_method_cashdro_fix``
(same method, resolved from the terminal instead of the selected line, raising
instead of returning ``false``). Once the upstream patch is merged, the
dependency has to be moved to ``pos_payment_method_cashdro`` and the
``_load_pos_data_fields`` override checked, as it is the only part of the other
module this one really needs.

Still open:

* The success path leaves the operation open on the drawer, as upstream does.
  Whether the CashDro3WS expects a ``finishOperation`` after a finished
  operation could not be checked without a machine, so the behaviour was left
  untouched.
* ``_cashdro_url()`` does not escape the user and the password, again as
  upstream does: credentials containing ``&``, ``=`` or ``#`` break the query
  string.
* The whole thing wants a tour with a mocked CashDro3WS endpoint, which would
  also let the OCA CI catch this class of breakage.