list sharing implemented w. passing UTs & FTs; changes to apps.dashboard.urls, .models, .views & .tests.test_views to accomodate; functional_tests.test_sharing also ensures sharing visible in UX; templates/apps/dashboard/list.html & /my_lists.html updated with django templating & for loops

src/apps/dashboard/views.py

@@ -37,3 +37,9 @@ def my_lists(request, user_id):
     if request.user.id != owner.id:
         return HttpResponseForbidden()
     return render(request, "apps/dashboard/my_lists.html", {"owner": owner})
+
+def share_list(request, list_id):
+    our_list = List.objects.get(id=list_id)
+    recipient = User.objects.get(email=request.POST["recipient"])
+    our_list.shared_with.add(recipient)
+    return redirect(our_list)