src/vs/workbench/common/views.ts/ViewContainersRegistryImpl/registerViewContainer
class ViewContainersRegistryImpl:	registerViewContainer(viewContainerDescriptor: IViewContainerDescriptor, viewContainerLocation: ViewContainerLocation, options?: { isDefault?: boolean, donotRegisterOpenCommand?: boolean }): ViewContainer {
		const existing = this.get(viewContainerDescriptor.id);
		if (existing) {
			return existing;
		}

		const viewContainer: RelaxedViewContainer = viewContainerDescriptor;
		viewContainer.openCommandActionDescriptor = options?.donotRegisterOpenCommand ? undefined : (viewContainer.openCommandActionDescriptor ?? { id: viewContainer.id });
		const viewContainers = getOrSet(this.viewContainers, viewContainerLocation, []);
		viewContainers.push(viewContainer);
		if (options?.isDefault) {
			this.defaultViewContainers.push(viewContainer);
		}
		this._onDidRegister.fire({ viewContainer, viewContainerLocation });
		return viewContainer;
	}