style Sylius#127 Refactor refund units command creator (Zales0123)

This PR was merged into the 1.0-dev branch.

Discussion
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Fixes Sylius#50 

It's now a little bit less complicated, I've got rid of this stupid `partial-id` attribute and extracted a service for better SRP respect.

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4a24d14 Exceptions refactoring + first input changes
d4343d9 UnitRefundTotalCalculator
9034720 Remodel refunds UI to use new command creator
4e05b73 Fixes after rebase

v0.6.0

- [Sylius#112](Sylius#112) Fix CreditMemo migration ([@Zales0123](https://github.com/Zales0123))
- [Sylius#113](Sylius#113) Use migrations in Travis ([@Zales0123](https://github.com/Zales0123))
- [Sylius#114](Sylius#114) Add branch-alias to composer.json ([@Zales0123](https://github.com/Zales0123))
- [Sylius#115](Sylius#115) Update to Sylius 1.4 ([@Zales0123](https://github.com/Zales0123))

minor Sylius#107 Symfony Messenger version updated (bartoszpietrzak1994)

This PR was merged into the 1.0-dev branch.

Discussion
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Commits
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acd737b Symfony Messenger version updated

Relate RefundPayment with Payment & bugfixes

- Relate `RefundPayment` with `Payment` [Sylius#85](Sylius#85)
- Support only offline payment methods [Sylius#86](Sylius#86)

- Partial refund inputs UI validation [Sylius#84](Sylius#84)
- Partial shipping refund display on credit memo [Sylius#94](Sylius#94)
- Remove unnecessary config for Sylius Mailer [Sylius#97](Sylius#97)

- Migrations namespace changed from `Sylius/Migrations` to `DoctrineMigrations` [Sylius#77](Sylius#77)
- "Fully refunded label" display improved [Sylius#81](Sylius#81)
- Partial refund inputs display improved [Sylius#84](Sylius#84)
- CODEOWNERS added [Sylius#88](Sylius#88)
- Security issues section added [Sylius#92](Sylius#92)
- Hide unneeded "refund" button [Sylius#96](Sylius#96)
- Switch from Prooph to Symfony Messenger [Sylius#89](Sylius#89)

Merge pull request Sylius#76 from Zales0123/refactor-refund-payment-c…

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🌊

Merge pull request Sylius#70 from Zales0123/bring-back-sylius-plugin-…

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📦

Merge pull request Sylius#69 from Zales0123/make-symfony-flex-comes-true

Change "sylius-plugin" to "symfony-bundle"

Merge pull request Sylius#67 from bartoszpietrzak1994/documentation-u…

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Documentation update

Merge pull request Sylius#52 from bartoszpietrzak1994/avoiding-channe…

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Filter name changed in sylius_grid

Merge pull request Sylius#20 from Zales0123/credit-memo-details-fix

CreditMemo details table fix