Issue #3483059 by tcrawford: Allow authentication with oAuth2 (grant type client credentials)

apisync.links.task.yml

apisync.routing.yml

apisync.services.yml

modules/apisync_basicauth/composer.json

...src/Plugin/ApiSyncAuthProvider/ApiSyncBasicAuthPlugin.php

..._basicauth/src/config/schema/apisync_basicauth.schema.yml

...les/apisync_mapping/src/ApiSyncMappingFieldPluginBase.php

...pisync_mapping/src/ApiSyncMappingFieldPluginInterface.php

modules/apisync_mapping/src/Entity/ApiSyncMappedObject.php

modules/apisync_mapping/src/Entity/ApiSyncMapping.php

...mapping/src/Plugin/ApiSyncMappingField/PropertiesBase.php

...ync_mapping/src/Plugin/ApiSyncMappingField/RelatedIDs.php

...ping/src/Plugin/ApiSyncMappingField/RelatedTermString.php

...s/apisync_mapping_ui/src/Form/ApiSyncMappedObjectForm.php

...es/apisync_mapping_ui/src/Form/ApiSyncMappingFormBase.php

...pisync_mapping_ui/src/Form/ApiSyncMappingFormCrudBase.php

modules/apisync_oauth/apisync_oauth.info.yml

modules/apisync_oauth/composer.json

...uth/src/Plugin/ApiSyncAuthProvider/ApiSyncOAuthPlugin.php

modules/apisync_pull/src/Plugin/QueueWorker/PullBase.php