chore: move executable code to src/

src/ now contains all source code - in subdirectories, according to the
.cabal component they belong to. This will allow us to put vendored
libraries in the same place - and later split our own code into multiple
components/libraries as well.

src/library/PostgREST/Auth.hs

@@ -0,0 +1,34 @@
+{-|
+Module      : PostgREST.Auth
+Description : PostgREST authentication functions.
+
+This module provides functions to deal with the JWT authentication (http://jwt.io).
+It also can be used to define other authentication functions,
+in the future Oauth, LDAP and similar integrations can be coded here.
+
+Authentication should always be implemented in an external service.
+In the test suite there is an example of simple login function that can be used for a
+very simple authentication system inside the PostgreSQL database.
+-}
+{-# LANGUAGE FlexibleContexts #-}
+module PostgREST.Auth
+  ( getAuthResult )
+  where
+
+import PostgREST.AppState      (AppState, getConfig, getJwtCacheState,
+                                getTime)
+import PostgREST.Auth.Jwt      (parseClaims)
+import PostgREST.Auth.JwtCache (lookupJwtCache)
+import PostgREST.Auth.Types    (AuthResult)
+import PostgREST.Error         (Error)
+
+import Protolude
+
+-- | Perform authentication and authorization
+--   Parse JWT and return AuthResult
+getAuthResult :: (MonadError Error m, MonadIO m) => AppState -> Maybe ByteString -> m AuthResult
+getAuthResult appState token = do
+  conf <- liftIO $ getConfig appState
+  time <- liftIO $ getTime appState
+
+  parseClaims conf time =<< lookupJwtCache (getJwtCacheState appState) token