The method that computs what is due and the change of an order is based
on the selected payment line which is wrong, because if you add and
remove a payment line, none will be seleced, that lead to issue in this
case because a change is computed, and it won't match the invoices
because an amount_return is sent to server.

To reproduce you can follow this simply procedure:
    - set rounding half-up to 0.05
    - create a product at 0.98
    - open POS and create an order with the product
    - go to payment screen
    - add cash payment (1€ auto filled)
    - add bank payment (It'll autofill -0.02 not really a problem)
    - remove the bank payment => It'll show 0.02 due (it is caused because of no payment method is selected)
    - Set a customer and check the invoice => unbalanced (0.02 probably because it is set in amount_return of the request)

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:




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Forward-Port-Of: odoo/odoo#70825

Potentially, users can add new fields using custom modules,
hence new columns.

It's therefore a good practice to fully qualify the columns
when defining a report view.

The case where the issue occurs is a 12.0 database
updating to 13.0 which has a column `product_id`
defined in another implied table than `sale_order_line`

```
2021-04-15 11:04:12,218 457 INFO db_8460 odoo.modules.registry: module sale_renting: creating or updating database tables
2021-04-15 11:04:12,329 457 ERROR db_8460 odoo.sql_db: bad query: CREATE or REPLACE VIEW sale_rental_report as (
        select
            sol.id,
            order_id,
            product_id,
            product_uom_qty  / (u.factor * u2.factor) as quantity,
            qty_delivered  / (u.factor * u2.factor) as qty_delivered,
            qty_returned  / (u.factor * u2.factor) as qty_returned,
            product_uom,
            order_partner_id as partner_id,
            salesman_id as user_id,
            categ_id,
            product_tmpl_id,
            generate_series(pickup_date::date, return_date::date, '1 day'::interval)::date date,
            price_subtotal / (date_part('day',return_date - pickup_date) + 1) as price,
            sol.company_id,
            sol.state,
            sol.currency_id
        from sale_order_line sol
            join product_product p on p.id=sol.product_id
            join product_template pt on p.product_tmpl_id=pt.id
            join uom_uom u on u.id=sol.product_uom
            join uom_uom u2 on u2.id=pt.uom_id
        where is_rental
        )
ERROR: column reference "product_id" is ambiguous
LINE 5:             product_id,
```

upg-15188

Forward-Port-Of: odoo/enterprise#18502

When consulting a signed document, if the user didn't complete some
optional fields, theses ones are still displayed with their placeholder
or field name as value

Note: This issue only happens on PDF preview. The downloaded PDF does
not contain any undesirable values.

To reproduce the issue:
1. In Sign, upload a PDF Template:
    - Add two fields:
        - Name
        - Text ("Mandatory field" disabled)
2. Sign Now
3. Complete Name, but not Text
4. Validate & Send Completed Document
5. Sign > Signatures, open signed document

Error: in the PDF viewer, the field Text is present on the document
(with value "Text"). It should not be present (The PDF provided by
"Download Document" button does not contain undesirable fields)

When the PDF is fully signed, a new document is generated and unfilled
fields are ignored. See in method `generate_completed_document`:
https://github.com/odoo/enterprise/blob/318da49017efbe0f2f9a045e022f601725d47f26/sign/models/sign_request.py#L468-L471
However, nothing prevents these fields to be rendered in the Sign
application viewer.

OPW-2479314

Forward-Port-Of: odoo/enterprise#18442
Forward-Port-Of: odoo/enterprise#18382