Allow overriding the file path for the books JSON file locally. Resolve a nullable chain code smell in the UI.

Author: jayjay2912

api/Services/BookService.cs

@@ -36,7 +36,10 @@ public ICollection<Book> GetBooks()
     private ICollection<Book> LoadBooks()
     {
         // try and load from the book JSON data source (it will be readonly until we have a database backing the service).
-        var path = Environment.GetEnvironmentVariable("HOME") + @"\site\wwwroot\books.json";
+        // locally, we can force the location of the file path using `ForceBooksFilePath` in `local.settings.json`.
+        // when running in a Function app, use the recommended path.
+        var path = Environment.GetEnvironmentVariable("ForceBooksFilePath") ??
+                   Environment.GetEnvironmentVariable("HOME") + @"\site\wwwroot\books.json";
         var books = JsonSerializer
             .Deserialize<ICollection<Book>>(File.ReadAllText(path)) ?? new List<Book>();
 

ui/src/app/pages/landing-page/landing-page.html

@@ -2,7 +2,7 @@
   <p-table
     #libraryTable
     [globalFilterFields]="['title', 'author', 'shelfLocation']"
-    [value]="library().books ?? []"
+    [value]="library().books"
     class="w-full"
     dataKey="title">
     <ng-template #caption>