Update the developer guide

This commit is fixing all non-functional links and updates the content to more up to date state.

It also removes fedmsg from the guide.

Signed-off-by: Michal Konečný <mkonecny@redhat.com>

modules/developer_guide/pages/auth.adoc

@@ -1,14 +1,11 @@
 == Authentication
 
-Fedora applications that require authentication should support, at a
-minimum, authentication against https://ipsilon-project.org/[Ipsilon].
-Ipsilon is an Identity Provider that uses a separate Identity Management
-system to perform authentication. In Fedora, Ipsilon is currently backed
-by the https://admin.fedoraproject.org/accounts/[Fedora Account System].
-In the future, it will be backed by http://www.freeipa.org/[FreeIPA].
+Fedora applications that require authentication should support
+https://accounts.fedoraproject.org/[Fedora Account System] backed
+by http://www.freeipa.org/[FreeIPA] as an identity provider.
 
-Ipsilon supports
-https://openid.net/specs/openid-authentication-2_0.html[OpenID 2.0],
+https://accounts.fedoraproject.org/[Fedora Account System] supports
+https://github.com/fedora-infra/fasjson/[fasjson] as read-only API,
 https://openid.net/connect/[OpenID Connect],
 https://tools.ietf.org/html/rfc6749[OAuth 2.0], and more.
 
@@ -17,7 +14,6 @@ https://tools.ietf.org/html/rfc6749[OAuth 2.0], and more.
 All new applications should use OpenID Connect for user authentication.
 
 [NOTE]
-.Note
 ====
 Many existing applications use OpenID 2.0 and should eventually migrate
 to OpenID Connect.
@@ -37,13 +33,11 @@ https://fedoraproject.org/wiki/Infrastructure/Authentication[Authentication
 Wiki page].
 
 [WARNING]
-.Warning
 ====
 OpenID Connect
 https://openid.net/specs/openid-connect-core-1_0.html#AuthRequest[requires
 that the "openid" scope is requested]. Failing to do so will result in
-undefined behavior. In the case of Ipsilon, you won't have access to the
-UserInfo or recieve an ID token.
+undefined behavior.
 ====
 
 === Libraries