payment 8.x-2.0-rc4

Remember to check the change records and to upgrade when coming from a previous release.

Migrating from Payment 7.x-1.x to 8.x-2.x is not yet supported in this version. See #2625626: [META] Migration from 7.x-1.x to 8.x-2.x.

Changes since 8.x-2.0-rc3:

• #2827793 by Berdir: PaymentStatusForm extends from EntityForm, submit fails with "container" is no valid field exception
• #2854938 by crasx: Refund button does not work in view operations
• #2878691 by nettantra: Error: Recoverable fatal error: Argument 1 passed to Drupal\Core\Field\Plugin\Field\FieldFormatter\EntityReferenceFormatterBase::getEntitiesToView
• #2913558 by mparker17: PaymentReference::preSave() assumes $unchanged_entity doesn't exist; fatal errors with "call to a member function get() on null" if $unchanged_entity exists and payment reference field is empty
• #2918680 by mparker17: Add refund tab to Payment entity view page
• #2940571 by Berdir: Update unit tests and entity form constructors
• Fix test failures (#36)
• #2630804 by Berdir, yongt9412: PaymentMethodBase::execute() tries to save a stale payment instance
• #2630808 by Berdir, yongt9412: Response::getResponse() does not collect cacheability metadata from Url object
• #2725805 by joshi.rohit100: \Drupal\payment\Entity\Payment\PaymentStatusForm::currentUser is accessed dynamically
• #2763385 by ricovandevin, Xano: The payment form should use the payment completion response and not just its URL
• #2763029 by Xano: Use Plugin's Plugin ID Views filter.
• #2763087: Fix our Composer version constraints and perform a Composer update for the Travis CI builds
• #2754115 by neerajsingh: Remove @file tag docblock