Add a CSV export functionality in admin and add price fields (#41)

* Implement an action do download data in csv
* Refactor CSV download
* Move price to main models and add csv to bookshelf
* Update template and API
* Small refactoring

ram/bookshelf/urls.py

@@ -1,7 +1,9 @@
 from django.urls import path
-from bookshelf.views import BookList, BookGet
+from bookshelf.views import BookList, BookGet, CatalogList, CatalogGet
 
 urlpatterns = [
     path("book/list", BookList.as_view()),
     path("book/get/<uuid:uuid>", BookGet.as_view()),
+    path("catalog/list", CatalogList.as_view()),
+    path("catalog/get/<uuid:uuid>", CatalogGet.as_view()),
 ]