website/docs: add application docs

closes #1837

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

website/docs/applications.md

@@ -0,0 +1,40 @@
+---
+title: Applications
+---
+
+Applications in authentik are the counterpart of providers. They exist in a 1-to-1 relationship, each application needs a provider and every provider can be used with one application.
+
+Applications are used to configure and separate the authorization / access control and the appearance in the Library page.
+
+## Authorization
+
+Application access can be configured using (Policy) Bindings. You can use this to grant access to one or multiple users/groups, or dynamically give access using policies.
+
+By default, all users can access applications when no policies are bound.
+
+When multiple policies/groups/users are attached, you can configure the *Policy engine mode* to either
+
+    - Require users to pass all bindings/be member of all groups (ALL), or
+    - Require users to pass either binding/be member of either group (ANY)
+
+## Appearance
+
+The following aspects can be configured:
+
+    - *Name*: This is the name shown for the application card
+    - *Launch URL*: The URL that is opened when a user clicks on the application. When left empty, authentik tries to guess it based on the provider
+    - *Icon (URL)*: Optionally configure an Icon for the application
+    - *Publisher*: Text shown below the application
+    - *Description*: Subtext shown on the application card below the publisher
+
+Applications are shown to users when
+
+    - The user has access defined via policies (or the application has no policies bound)
+    - A Valid Launch URL is configured/could be guessed, this consists of URLs starting with http:// and https://
+
+
+#### Hiding applications
+
+To hide applications without modifying policy settings and without removing it, you can simply set the *Launch URL* to `blank://blank`, which will hide the application from users.
+
+Keep in mind, the users still have access, so they can still authorize access when the login process is started from the application.