feat: type not editable

lib/membership/custom_field.ex

@@ -10,7 +10,7 @@ defmodule Mv.Membership.CustomField do
   ## Attributes
   - `name` - Unique identifier for the custom field (e.g., "phone_mobile", "birthday")
   - `slug` - URL-friendly, immutable identifier automatically generated from name (e.g., "phone-mobile")
-  - `value_type` - Data type constraint (`:string`, `:integer`, `:boolean`, `:date`, `:email`)
+  - `value_type` - Data type constraint (`:string`, `:integer`, `:boolean`, `:date`, `:email`). Immutable after creation.
   - `description` - Optional human-readable description
   - `required` - If true, all members must have this custom field (future feature)
   - `show_in_overview` - If true, this custom field will be displayed in the member overview table and can be sorted
@@ -28,6 +28,7 @@ defmodule Mv.Membership.CustomField do
   ## Constraints
   - Name must be unique across all custom fields
   - Name maximum length: 100 characters
+  - `value_type` cannot be changed after creation (immutable)
   - Deleting a custom field will cascade delete all associated custom field values
 
   ## Calculations
@@ -59,7 +60,7 @@ defmodule Mv.Membership.CustomField do
   end
 
   actions do
-    defaults [:read, :update]
+    defaults [:read]
     default_accept [:name, :value_type, :description, :required, :show_in_overview]
 
     create :create do
@@ -68,6 +69,21 @@ defmodule Mv.Membership.CustomField do
       validate string_length(:slug, min: 1)
     end
 
+    update :update do
+      accept [:name, :description, :required, :show_in_overview]
+      require_atomic? false
+
+      validate fn changeset, _context ->
+        if Ash.Changeset.changing_attribute?(changeset, :value_type) do
+          {:error,
+           field: :value_type,
+           message: "cannot be changed after creation"}
+        else
+          :ok
+        end
+      end
+    end
+
     destroy :destroy_with_values do
       primary? true
     end