Add leaking values

elm.json

@@ -8,6 +8,7 @@
         "Matrix",
         "Matrix.Settings",
         "Internal.Config.Default",
+        "Internal.Config.Leaks",
         "Internal.Config.Text",
         "Internal.Tools.Decode",
         "Internal.Tools.Encode",

src/Internal/Config/Leaks.elm

@@ -0,0 +1,39 @@
+module Internal.Config.Leaks exposing (accessToken)
+
+{-|
+
+
+# Leaks module
+
+The Elm compiler is quite picky when it comes to handling edge cases, which may
+occasionally result in requiring us to insert values in impossible states.
+
+This module offers placeholders for those times. The placeholder values are
+intentionally called "leaks", because they should be used carefully: a wrongful
+implementation might cause unexpected behaviour, vulnerabilities or even
+security risks!
+
+You should not use this module unless you know what you're doing. That is:
+
+  - By exclusively using leaking values in opaque types so a user cannot
+    accidentally reach an impossible state
+  - By exclusively using leaking values in cases where the compiler is the only
+    reason that the leaking value needs to be used
+  - By exclusively using leaking values if there is no way to circumvent the
+    compiler with a reasonable method.
+
+One such example would be to turn an `Maybe Int` into an `Int` if you already
+know 100% sure that the value isn't `Nothing`.
+
+    Just 5 |> Maybe.withDefault Leaks.number
+
+@docs accessToken
+
+-}
+
+
+{-| Placeholder access token.
+-}
+accessToken : String
+accessToken =
+    "elm-sdk-placeholder-access-token-leaks"