Merge extension_attributes on addressInformation. When this is not do…

[ldrooij]

Merge extension_attributes on addressInformation. When this is done extension_attributes from other modules will be overwritten instead of being merged

Description (*)

We ran into an issue where extension_attributes added by other modules on addressInformation during shipping data storage in check-out were overwritten when the payload was modified. Merging the extension_attributes instead of replacing them fixes the issue

Manual testing scenarios (*)

1. Install module that modifies extension_attributes payload. In the example of module amasty deliverydate manager the selected delivery date and pick-up slot were not stores. (We know the module offers functions for this, but we required additional logic for this).
2. Complete an order. All the additional data should be saved on the order.

Contribution checklist (*)

• [x] Pull request has a meaningful description of its purpose
• [x] All commits are accompanied by meaningful commit messages
• [x] All new or changed code is covered with unit/integration tests (if applicable)
• [x] All automated tests passed successfully (all builds are green)

[lsretailomni]

@ldrooij thanks for reporting, this is already included in release 2.2.0