Use deferred for action dispatcher initialization

[tortmayr]

What it does

Fixes a problem in the action dispatcher initialization that was introduced with #402.
Due to the change from async registry provider to direct registry injection it was possible to end up in a dead lock if there was an action handler was registered that listened to the SetModelAction and dispatches a response action.
(This handler would already been triggered during the initialization phase because an empty set model action is dispatched there, the corresponding initializationPromise was not defined at this point -> initialize logic is called again).

Solved by using a proper deferred for the initialization step.

How to test

Should not be required as the change is rather simple and straightforward. However, if needed this can be done by registering a custom action handler in the standalone app:

export default function createContainer(options: IDiagramOptions): Container {
    const parameters = getParameters();
    if (parameters.readonly) {
        options.editMode = EditMode.READONLY;
    }
    const container = createWorkflowDiagramContainer(
        createDiagramOptionsModule(options),
        {
            add: [standaloneTaskEditorModule, accessibilityModule],
            remove: toolPaletteModule
        },
        STANDALONE_MODULE_CONFIG
    );
    bindOrRebind(container, TYPES.ILogger).to(ConsoleLogger).inSingletonScope();
    bindOrRebind(container, TYPES.LogLevel).toConstantValue(LogLevel.warn);
    container.bind(TYPES.IMarqueeBehavior).toConstantValue({ entireEdge: true, entireElement: true });
    if (parameters.inversifyLog) {
        configureInversifyLogger(container);
    }
    configureActionHandler(container, SetModelAction.KIND, TestHandler);
    return container;
}

@injectable()
export class TestHandler implements IActionHandler {
    handle(action: Action): void | Action | ICommand {
        return OptionalAction.mark({ kind: 'test' });
    }
}

Observe that with this handler the application loading fails on master, but still works in this PR.

Follow-ups

Changelog

• This PR should be mentioned in the changelog
• This PR introduces a breaking change (if yes, provide more details below for the changelog and the migration guide)

[martin-fleck-at]

LGTM!