feat(backend): Added skeleton for a database learning object/path provider.

backend/src/services/learning-paths/database-learning-path-provider.ts

@@ -0,0 +1,23 @@
+import {LearningPathProvider} from "./learning-path-provider";
+import {LearningPath, LearningPathResponse} from "../../interfaces/learning-content";
+
+/**
+ * Service providing access to data about learning paths from the database.
+ */
+const databaseLearningPathProvider: LearningPathProvider = {
+    /**
+     * Fetch the learning paths with the given hruids from the database.
+     */
+    fetchLearningPaths(hruids: string[], language: string, source: string): Promise<LearningPathResponse> {
+        throw new Error("Not yet implemented"); // TODO
+    },
+
+    /**
+     * Search learning paths in the database using the given search string.
+     */
+    searchLearningPaths(query: string, language: string): Promise<LearningPath[]> {
+        return Promise.resolve([]); // TODO
+    }
+}
+
+export default databaseLearningPathProvider;