Add internal Vault type

elm.json

@@ -14,7 +14,9 @@
         "Internal.Tools.Iddict",
         "Internal.Tools.Timestamp",
         "Internal.Tools.VersionControl",
-        "Internal.Values.Envelope"
+        "Internal.Values.Envelope",
+        "Internal.Values.Vault",
+        "Types"
     ],
     "elm-version": "0.19.0 <= v < 0.20.0",
     "dependencies": {

src/Internal/Values/Vault.elm

@@ -0,0 +1,15 @@
+module Internal.Values.Vault exposing (Vault)
+
+{-| This module hosts the Vault module.
+
+@docs Vault
+
+-}
+
+import Internal.Values.Envelope as Envelope
+
+
+{-| This is the Vault type.
+-}
+type alias Vault =
+    Envelope.Envelope {}

src/Types.elm

@@ -0,0 +1,25 @@
+module Types exposing (Vault(..))
+
+{-| The Elm SDK uses a lot of records and values that are easy to manipulate.
+Yet, the [Elm design guidelines](https://package.elm-lang.org/help/design-guidelines#keep-tags-and-record-constructors-secret)
+highly recommend using opaque types in order to avoid breaking everyone's code
+in a future major release.
+
+This module forms as a protective layer between the internal modules and the
+exposed modules, hiding all exposed types behind opaque types so the user cannot
+access their content directly.
+
+The opaque types are placed in a central module so all exposed modules can
+safely access all exposed data types without risking to create circular imports.
+
+@docs Vault
+
+-}
+
+import Internal.Values.Vault as Vault
+
+
+{-| Opaque type for Matrix Vault
+-}
+type Vault
+    = Vault Vault.Vault