[server] Move server-related files into their own subdirectory

src/Forest/Server/TreeModule.hs

@@ -0,0 +1,25 @@
+{-# LANGUAGE MultiParamTypeClasses #-}
+
+module Forest.Server.TreeModule
+  ( TreeModule(..)
+  , ModuleConstructor
+  ) where
+
+import qualified Data.Text   as T
+
+import           Forest.Node
+
+class TreeModule a r where
+  edit :: a r -> Path -> T.Text -> IO (Maybe r)
+  edit _ _ _ = pure Nothing
+
+  delete :: a r -> Path -> IO (Maybe r)
+  delete _ _ = pure Nothing
+
+  reply :: a r -> Path -> T.Text -> IO (Maybe r)
+  reply _ _ _ = pure Nothing
+
+  act :: a r -> Path -> IO (Maybe r)
+  act _ _ = pure Nothing
+
+type ModuleConstructor a = (Node -> IO ()) -> (a -> IO ()) -> IO ()