Update view to use different imports/decorators

1. We can generally expect the json module to be
   available now, so no need to use what ships with
   django
2. require_POST is just simpler and more direct
3. Using login_required is clearer as well instead
   of using custom logic.

kaleo/views.py

@@ -1,18 +1,18 @@
+import json
+
 from django import http
-from django.utils import simplejson as json
-from django.views.decorators.http import require_http_methods
+from django.views.decorators.http import require_POST
 
 from account.models import EmailAddress
+from django.contrib.auth.decorators import login_required
 
 from kaleo.forms import InviteForm
 from kaleo.models import JoinInvitation
 
 
-@require_http_methods(["POST"])
+@login_required
+@require_POST
 def invite(request):
-    if not request.user.is_authenticated():
-        data = {"status": "ERROR", "message": "not authenticated"}
-        return http.HttpResponseBadRequest(json.dumps(data), content_type="application/json")
     form = InviteForm(request.POST)
     if form.is_valid():
         email = form.cleaned_data["email_address"]