Update cookbook-plain app requirements and local-dev notes

This also adds the DEFAULT_AUTO_FIELD to the app's Django settings to
resolve this warning when running `migrate`:

```
ingredients.Category: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
	HINT: Configure the DEFAULT_AUTO_FIELD setting or the IngredientsConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
```

examples/cookbook-plain/README.md

@@ -62,3 +62,12 @@ Now head on over to
 and run some queries!
 (See the [Graphene-Django Tutorial](http://docs.graphene-python.org/projects/django/en/latest/tutorial-plain/#testing-our-graphql-schema)
 for some example queries)
+
+Testing local graphene-django changes
+-------------------------------------
+
+In `requirements.txt`, replace the entire `graphene-django=...` line with the following (so that we install the local version instead of the one from PyPI):
+
+```
+../../  # graphene-django
+```

examples/cookbook-plain/cookbook/settings.py

@@ -5,10 +5,10 @@ Django settings for cookbook project.
 Generated by 'django-admin startproject' using Django 1.9.
 
 For more information on this file, see
-https://docs.djangoproject.com/en/1.9/topics/settings/
+https://docs.djangoproject.com/en/3.2/topics/settings/
 
 For the full list of settings and their values, see
-https://docs.djangoproject.com/en/1.9/ref/settings/
+https://docs.djangoproject.com/en/3.2/ref/settings/
 """
 
 import os
@@ -18,7 +18,7 @@ BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
 
 # Quick-start development settings - unsuitable for production
-# See https://docs.djangoproject.com/en/1.9/howto/deployment/checklist/
+# See https://docs.djangoproject.com/en/3.2/howto/deployment/checklist/
 
 # SECURITY WARNING: keep the secret key used in production secret!
 SECRET_KEY = "_$=$%eqxk$8ss4n7mtgarw^5$8^d5+c83!vwatr@i_81myb=e4"
@@ -81,7 +81,7 @@ WSGI_APPLICATION = "cookbook.wsgi.application"
 
 
 # Database
-# https://docs.djangoproject.com/en/1.9/ref/settings/#databases
+# https://docs.djangoproject.com/en/3.2/ref/settings/#databases
 
 DATABASES = {
     "default": {
@@ -90,9 +90,11 @@ DATABASES = {
     }
 }
 
+# https://docs.djangoproject.com/en/3.2/ref/settings/#default-auto-field
+DEFAULT_AUTO_FIELD = "django.db.models.AutoField"
 
 # Password validation
-# https://docs.djangoproject.com/en/1.9/ref/settings/#auth-password-validators
+# https://docs.djangoproject.com/en/3.2/ref/settings/#auth-password-validators
 
 AUTH_PASSWORD_VALIDATORS = [
     {
@@ -105,7 +107,7 @@ AUTH_PASSWORD_VALIDATORS = [
 
 
 # Internationalization
-# https://docs.djangoproject.com/en/1.9/topics/i18n/
+# https://docs.djangoproject.com/en/3.2/topics/i18n/
 
 LANGUAGE_CODE = "en-us"
 
@@ -119,6 +121,6 @@ USE_TZ = True
 
 
 # Static files (CSS, JavaScript, Images)
-# https://docs.djangoproject.com/en/1.9/howto/static-files/
+# https://docs.djangoproject.com/en/3.2/howto/static-files/
 
 STATIC_URL = "/static/"

examples/cookbook-plain/requirements.txt

@@ -1,4 +1,3 @@
-graphene>=2.1,<3
+django~=3.2
-graphene-django>=2.1,<3
+graphene
-graphql-core>=2.1,<3
+graphene-django>=3.1
-django==3.1.14