refactor(users/glittershark): Rename to grfn

Rename my //users directory and all places that refer to glittershark to
grfn, including nix references and documentation.

This may require some extra attention inside of gerrit's database after
it lands to allow me to actually push things.

Change-Id: I4728b7ec2c60024392c1c1fa6e0d4a59b3e266fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2933
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Reviewed-by: glittershark <grfn@gws.fyi>

users/grfn/xanthous/test/Xanthous/Data/EntityMap/GraphicsSpec.hs

@@ -0,0 +1,57 @@
+--------------------------------------------------------------------------------
+module Xanthous.Data.EntityMap.GraphicsSpec (main, test) where
+--------------------------------------------------------------------------------
+import Test.Prelude
+import Data.Aeson
+--------------------------------------------------------------------------------
+import Xanthous.Game.State
+import Xanthous.Data
+import Xanthous.Data.EntityMap
+import Xanthous.Data.EntityMap.Graphics
+import Xanthous.Entities.Environment (Wall(..))
+--------------------------------------------------------------------------------
+
+main :: IO ()
+main = defaultMain test
+
+test :: TestTree
+test = testGroup "Xanthous.Data.EntityMap.Graphics"
+  [ testGroup "visiblePositions"
+    [ testProperty "one step in each cardinal direction is always visible"
+      $ \pos (Cardinal dir) (Positive r) (wallPositions :: Set Position)->
+          pos `notMember` wallPositions ==>
+          let em = review _EntityMap . map (, Wall) . toList $ wallPositions
+              em' = em & atPosition (move dir pos) %~ (Wall <|)
+              poss = visiblePositions pos r em'
+          in counterexample ("visiblePositions: " <> show poss)
+             $ move dir pos `member` poss
+    , testGroup "bugs"
+      [ testCase "non-contiguous bug 1"
+        $ let charPos = Position 20 20
+              gormlakPos = Position 17 19
+              em = insertAt gormlakPos TestEntity
+                   . insertAt charPos TestEntity
+                   $ mempty
+              visPositions = visiblePositions charPos 12 em
+          in (gormlakPos `member` visPositions) @?
+             ( "not ("
+             <> show gormlakPos <> " `member` "
+             <> show visPositions
+             <> ")"
+             )
+      ]
+    ]
+  ]
+
+--------------------------------------------------------------------------------
+
+data TestEntity = TestEntity
+  deriving stock (Show, Eq, Ord, Generic)
+  deriving anyclass (ToJSON, FromJSON, NFData)
+
+instance Brain TestEntity where
+  step _ = pure
+instance Draw TestEntity
+instance Entity TestEntity where
+  description _ = ""
+  entityChar _ = "e"