Started auth/validation docs.

docs/developers/auth.rst

@@ -0,0 +1,3 @@
+===================
+User Authentication
+===================

docs/developers/index.rst

@@ -41,3 +41,5 @@ Following references cover everything you want to know about writing your own ap
    cache
    cache_buster
    thread_store
+   validators
+   auth

docs/developers/validators.rst

@@ -0,0 +1,5 @@
+=================
+Misago Validators
+=================
+
+Misago apps implement plenty of validators, wich so

docs/index.rst

@@ -30,3 +30,5 @@ Table of Contents
    developers/cache
    developers/cache_buster
    developers/thread_store
+   developers/validators
+   developers/auth