Parse Error - PHP 7.4

Problem/Motivation

This module is unusable on PHP 7.4, installation causes the following error when trying to add a server.

The website encountered an unexpected error. Please try again later.
ParseError: syntax error, unexpected '=>' (T_DOUBLE_ARROW) in Composer\Autoload\includeFile() (line 137 of modules/contrib/search_api_opensearch/src/SearchAPI/Query/FilterBuilder.php).
Composer\Autoload\includeFile('/var/www/html/web/modules/contrib/search_api_opensearch/src/SearchAPI/Query/FilterBuilder.php') (Line: 428)
Composer\Autoload\ClassLoader->loadClass('Drupal\search_api_opensearch\SearchAPI\Query\FilterBuilder')
spl_autoload_call('Drupal\search_api_opensearch\SearchAPI\Query\FilterBuilder') (Line: 262)
Drupal\Component\DependencyInjection\Container->createService(Array, 'search_api_opensearch.query_filter_builder') (Line: 176)
Drupal\Component\DependencyInjection\Container->get('search_api_opensearch.query_filter_builder', 1) (Line: 437)
Drupal\Component\DependencyInjection\Container->resolveServicesAndParameters(Array) (Line: 240)
Drupal\Component\DependencyInjection\Container->createService(Array, 'search_api_opensearch.query_param_builder') (Line: 176)
Drupal\Component\DependencyInjection\Container->get('search_api_opensearch.query_param_builder', 1) (Line: 437)
Drupal\Component\DependencyInjection\Container->resolveServicesAndParameters(Array) (Line: 240)
Drupal\Component\DependencyInjection\Container->createService(Array, 'search_api_opensearch.backend_client_factory') (Line: 176)
Drupal\Component\DependencyInjection\Container->get('search_api_opensearch.backend_client_factory') (Line: 89)
Drupal\search_api_opensearch\Plugin\search_api\backend\OpenSearchBackend::create(Object, Array, 'opensearch', Array) (Line: 21)
Drupal\Core\Plugin\Factory\ContainerFactory->createInstance('opensearch', Array) (Line: 83)
Drupal\Component\Plugin\PluginManagerBase->createInstance('opensearch', Array) (Line: 148)
Drupal\search_api\Form\ServerForm->buildEntityForm(Array, Object, Object) (Line: 85)
Drupal\search_api\Form\ServerForm->form(Array, Object) (Line: 106)
Drupal\Core\Entity\EntityForm->buildForm(Array, Object)
call_user_func_array(Array, Array) (Line: 532)
Drupal\Core\Form\FormBuilder->retrieveForm('search_api_server_form', Object) (Line: 278)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object) (Line: 39)
Drupal\layout_builder\Controller\LayoutBuilderHtmlEntityFormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 578)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 158)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 80)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 717)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes