Description of the issue/feature this PR addresses:
fixes #11386
Current behavior before PR:
Some taxes were taken into account when calculating residual on invoices. Those taxes however are not due to the invoice partner but shall be paid to the tax authority.
Desired behavior after PR is merged:
Now a tax can be configured so that a partner (eg. tax authority) can be defined on the tax. If such partner is defined on a specific tax, the move line of this tax will contain the newly configured partner (eg tax authority). Furthermore residual calculation will evaluate this and not sum tax values, even if they have been registered on a receivable or payable account.
As a nice side effect, reconciliation of tax payments will now be automatic, as partner on bank statement (eg tax authrity) and partner on moveline (eg tax authority) coincide.

"eg tax authority" can be exactly this, or any other collecting entity, such as municipalities, environmental agencies, half public agencies, etc.

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add partner to tax lines and restrict residual calculus on invoice partner lines.
Before tax lines had the same partner_id as the invoice_id
which made the residual calc only dependent on the account type.
However exist valid business cases, where also tax are registered
on the recievable/payable types (the ones that where taken into account
by the residual caluculs)
This module not only solves this case by allowing to put a partner_id
on tax groups, which is then propagated to the move line partner_id.
It also allows for more automated reconciliation as the bank statement lines
which have the tax authority registered get reconciled automatically.
RISK: It might be, that some tax reportings rely on the invoice partner_id
beeing available on the tax' move line partner_id directly (as a shortcut for
line.invoice_id.partner_id). This, however can be considered as bad practice
because there is a conceptual mismatch between what a partner_id of a
payable normally tells us, and what it tells us in case of taxes.

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