thumbor: Auto generate thumbor_key and add it to zulip settings.

scripts/setup/generate_secrets.py

@@ -30,6 +30,7 @@ AUTOGENERATED_SETTINGS = [
     'local_database_password',
     'rabbitmq_password',
     'shared_secret',
+    'thumbor_key',
 ]
 
 # TODO: We can eliminate this function if we refactor the install

version.py

@@ -1,2 +1,2 @@
 ZULIP_VERSION = "1.7.0+git"
-PROVISION_VERSION = '11.3'
+PROVISION_VERSION = '11.4'

zproject/settings.py

@@ -1484,3 +1484,5 @@ CROSS_REALM_BOT_EMAILS = {
 }
 
 CONTRIBUTORS_DATA = os.path.join(STATIC_ROOT, 'generated/github-contributors.json')
+
+THUMBOR_KEY = get_secret('thumbor_key')