website/docs: update and rearchitect the oauth2 provider docs (#11916)

* new topics

* update diagram

* more writing and sidebar entries

* fix file name

* more link fixes

* fix header level

* Optimised images with calibre/image-actions

* rewrite stuff

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

* reorganize more

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

* messed w/ diagram and added 3 categories

* fixed anchor

* removed whole line

* add link

* more rearrangements

* more content

* edits

* more polishes, rest of Jens' knowledge dump

* more content

* tweaks

* tweak

* argh

* synch with main

* tweaks to test merge

* cleanup

* offline_access

* polish

---------

Signed-off-by: Jens Langhammer <jens@goauthentik.io>
Co-authored-by: Tana M Berry <tana@goauthentik.com>
Co-authored-by: authentik-automation[bot] <135050075+authentik-automation[bot]@users.noreply.github.com>
Co-authored-by: Jens Langhammer <jens@goauthentik.io>

website/sidebars.js

@@ -193,8 +193,10 @@ export default {
                                 id: "add-secure-apps/providers/oauth2/index",
                             },
                             items: [
+                                "add-secure-apps/providers/oauth2/create-oauth2-provider",
                                 "add-secure-apps/providers/oauth2/client_credentials",
                                 "add-secure-apps/providers/oauth2/device_code",
+                                "add-secure-apps/providers/oauth2/github-compatibility",
                             ],
                         },
                         "add-secure-apps/providers/saml/index",