[ready now, #4603 almost done] Allow to get multiple cms components data in one request

Feature request (discussed with @WeizhengSap on Slack):

For now in CmsService.getComponentData we can get one component’s data via its uid. This method prepares request to OCC and saves response as component data in the store and returns an observable with such chain.

However, for navigation there is a custom method to fetch multiple navigation node components in one request (see NavigationEntryItemEffects and CmsComponentConnector.getList).

What we miss here is to have a method like CmsService.getComponentsData which will get a list of uids of component and prepare one request to OCC for multiple components data.

[Xymmer]

@artem-zur it’s doable so we’ll try

[znikola]

getComponentData method can be safely and optimally used to load multiple components data at the same time. Calling getComponentData multiple times for different components will always result in optimized back-end request: all components requested at the same time (in one event loop) will be loaded in one network call.

Therefore, closing this issue for now, as there’s no need to add a new method.