Adding GetSaveableNewsResourcesUseCase

GetSaveableNewsResourcesUseCase.kt

/* Copyright 2022 Google LLC.	
   SPDX-License-Identifier: Apache-2.0 */

class GetSaveableNewsResourcesUseCase @Inject constructor(
    private val newsRepository: NewsRepository,
    userDataRepository: UserDataRepository
) {
    private val bookmarks = userDataRepository.userDataStream.map { userData -> 
        userData.bookmarkedNewsResources
    }

    operator fun invoke(): Flow<List<SaveableNewsResource>> =
        newsRepository.getNewsResources()
            .combine(bookmarks) { newsResources, bookmarks ->
                newsResources.map { newsResource ->
                    SaveableNewsResource(
                        newsResource = newsResource,
                        isSaved = bookmarks.contains(newsResource.id)
                    )
                }
            }
}