feat: property value as Union type

lib/membership/property.ex

@@ -16,8 +16,16 @@ defmodule Mv.Membership.Property do
   attributes do
     uuid_primary_key :id
 
-    attribute :value, :string,
-      description: "Speichert den Wert, Typ-Interpretation per property_type.typ"
+    attribute :value, :union,
+      constraints: [
+        storage: :type_and_value,
+        types: [
+          bool: [type: :boolean],
+          date: [type: :date],
+          int: [type: :integer],
+          string: [type: :string]
+        ]
+      ]
   end
 
   relationships do
@@ -25,4 +33,8 @@ defmodule Mv.Membership.Property do
 
     belongs_to :property_type, Mv.Membership.PropertyType
   end
+
+  calculations do
+    calculate :value_to_string, :string, expr(value[:value] <> "")
+  end
 end