Fix missing signature when certifying

src/sakia/data/processors/certifications.py

src/sakia/gui/dialogs/certification/controller.py

src/sakia/gui/dialogs/transfer/controller.py

src/sakia/gui/main_window/toolbar/model.py

src/sakia/gui/navigation/graphs/base/controller.py

src/sakia/gui/navigation/graphs/base/node.py

src/sakia/gui/navigation/graphs/base/scene.py

src/sakia/gui/widgets/context_menu.py

src/sakia/services/documents.py