run tests against django 5.1

tox.ini

@@ -1,9 +1,9 @@
 [tox]
 isolated_build = true
 envlist =
-    py{37,38,39}-django-{32}
-    py{38,39,310,311}-django-{42}
-    py{310,311,312}-django-{50}
+    py{38,39,310,311}-django{42}
+    py{310,311,312}-django{50}
+    py{310,311,312}-django{51}
 
 [gh-actions]
 python =
@@ -22,9 +22,9 @@ setenv =
 
 commands = coverage run --source contentful_webhook_receiver runtests.py
 deps =
-    django-32: Django>=3.2,<4.0
-    django-42: Django>=4.2,<4.3
-    django-50: Django>=5.0,<5.1
+    django42: Django>=4.2,<4.3
+    django50: Django>=5.0,<5.1
+    django51: Django>=5.1,<5.2
 
 
 basepython =