9 files declare their use of WorkspaceInterface in Drupal 9

content_moderation.module in core/modules/content_moderation/content_moderation.module

Contains content_moderation.module.

SessionWorkspaceNegotiator.php in core/modules/workspaces/src/Negotiator/SessionWorkspaceNegotiator.php

TestWorkspaceNegotiator.php in core/modules/workspaces/tests/modules/workspace_update_test/src/Negotiator/TestWorkspaceNegotiator.php

Workspace.php in core/modules/workspaces/src/Entity/Workspace.php

WorkspaceMergeForm.php in core/modules/workspaces/src/Form/WorkspaceMergeForm.php

WorkspaceNegotiatorInterface.php in core/modules/workspaces/src/Negotiator/WorkspaceNegotiatorInterface.php

WorkspacePublishForm.php in core/modules/workspaces/src/Form/WorkspacePublishForm.php

WorkspaceRequestSubscriberTest.php in core/modules/workspaces/tests/src/Unit/WorkspaceRequestSubscriberTest.php

WorkspaceTestUtilities.php in core/modules/workspaces/tests/src/Functional/WorkspaceTestUtilities.php