stages/identification: make shown sources configurable

closes #918

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

website/docs/releases/next.md

@@ -0,0 +1,27 @@
+---
+title: Next
+---
+
+## Headline Changes
+
+- Duo two-factor support
+
+    You can now add the new `authenticator_duo` stage to configure Duo authenticators. Duo has also been added as device class to the `authenticator_validation` stage.
+
+    Currently, only Duo push notifications are supported. Because no additional input is required, Duo also works with the LDAP Outpost.
+
+## Minor changes
+
+- You can now specify which sources should be shown on an Identification stage.
+
+## Upgrading
+
+This release does not introduce any new requirements.
+
+### docker-compose
+
+Download the docker-compose file for 2021.6 from [here](https://raw.githubusercontent.com/goauthentik/authentik/version-2021.6/docker-compose.yml). Afterwards, simply run `docker-compose up -d`.
+
+### Kubernetes
+
+Upgrade to the latest chart version to get the new images.