Currently, when validating an order, an error appears.

Steps to reproduce:
-------------------
* Install **l10n_de_pos_cert** and set up **fiskaly**
* Set up **PoS** in German company
* Open a store session
* Validate an order
> Unknown Error: An unknown error has occured! Please, contact Odoo.

Why the fix:
------------
https://github.com/odoo/enterprise/blob/a8bd649f7b4c5c3af64edaca19b9c8ca9999cd9e/l10n_de_pos_cert/static/src/overrides/models/models.js#L184-L186

Function `get_tax_details()` was changed with
https://github.com/odoo/odoo/commit/ab0bdf0192120671010634978f202da35ddfc79f

It was previously returning an object of the form
```js
amount: 56.050000000000004
base: 295
name: "19%"
tax: Proxy(AccountTax)
    amount: 19
    amount_type: "percent"
    children_tax_ids: []
    company_id: Base {models: {…}, records: Proxy(Object), model: {…}, _raw: {…}, id: 3, …}
    id: 16
    include_base_amount: false
    is_base_affected: true
    model: {…}
    models: {pos.config: {…}, pos.order: {…}, pos.order.line: {…}, pos.session: {…}, pos.payment.method: {…}, …}
    name: "19%"
    price_include: false
```

And now returns
```js
amount: 56.050000000000004
amount_type: "percent"
base: 295
batch_indexes: [0]
display_base: 295
evaluation_context: {multiplicator: 0.19}
extra_base_for_base: []
extra_base_for_tax: []
id: 16
include_base_amount: false
index: 0
is_base_affected: true
name: "19%"
price_include: false
sequence: 10
tag_ids: []
tax_amount: 56.05
tax_amount_factorized: 56.050000000000004
tax_exigibility: "on_invoice"
tax_ids: []
tax_percentage: 19
```

`details.tax.id` is now simply `details.id` and `details.tax.amount` is `details.tax_percentage`. As per the following definition: https://github.com/odoo/odoo/blob/5058c01974431af1cb3a59d65bf40cf5b08ba4ea/addons/point_of_sale/static/src/app/store/models.js#L2202-L2209

opw-3924715