Add stubs for fetching articles for starred and today feeds.

Evergreen/SmartFeeds/SmartFeed.swift

@@ -11,7 +11,7 @@ import RSCore
 import Data
 import Account
 
-protocol SmartFeedDelegate: DisplayNameProvider {
+protocol SmartFeedDelegate: DisplayNameProvider, ArticleFetcher {
 
 	func fetchUnreadCount(for: Account, callback: @escaping (Int) -> Void)
 }
@@ -51,6 +51,19 @@ final class SmartFeed: PseudoFeed {
 	}
 }
 
+extension SmartFeed: ArticleFetcher {
+
+	func fetchArticles() -> Set<Article> {
+
+		return delegate.fetchArticles()
+	}
+
+	func fetchUnreadArticles() -> Set<Article> {
+
+		return delegate.fetchUnreadArticles()
+	}
+}
+
 private extension SmartFeed {
 
 	// MARK: - Unread Counts

Evergreen/SmartFeeds/StarredFeedDelegate.swift

@@ -19,4 +19,18 @@ struct StarredFeedDelegate: SmartFeedDelegate {
 
 		account.fetchUnreadCountForStarredArticles(callback)
 	}
+
+	// MARK: ArticleFetcher
+
+	func fetchArticles() -> Set<Article> {
+
+		// TODO
+		return Set<Article>()
+	}
+
+	func fetchUnreadArticles() -> Set<Article> {
+
+		return fetchArticles().unreadArticles()
+	}
+
 }

Evergreen/SmartFeeds/TodayFeedDelegate.swift

@@ -18,5 +18,18 @@ struct TodayFeedDelegate: SmartFeedDelegate {
 
 		account.fetchUnreadCountForToday(callback)
 	}
+
+	// MARK: ArticleFetcher
+
+	func fetchArticles() -> Set<Article> {
+
+		// TODO
+		return Set<Article>()
+	}
+
+	func fetchUnreadArticles() -> Set<Article> {
+
+		return fetchArticles().unreadArticles()
+	}
 }