chore: adds settings ressource and migration

lib/membership/setting.ex

@@ -0,0 +1,80 @@
+defmodule Mv.Membership.Setting do
+  @moduledoc """
+  Ash resource representing global application settings.
+
+  ## Overview
+  Settings is a singleton resource that stores global configuration for the association,
+  such as the club name and branding information. There should only ever be one settings
+  record in the database.
+
+  ## Attributes
+  - `club_name` - The name of the association/club (required, cannot be empty)
+
+  ## Singleton Pattern
+  This resource uses a singleton pattern - there should only be one settings record.
+  The resource is designed to be read and updated, but not created or destroyed
+  through normal CRUD operations. Initial settings should be seeded.
+
+  ## Environment Variable Support
+  The `club_name` can be set via the `ASSOCIATION_NAME` environment variable.
+  If set, the environment variable value is used as a fallback when no database
+  value exists. Database values always take precedence over environment variables.
+
+  ## Examples
+
+      # Get current settings
+      {:ok, settings} = Mv.Membership.get_settings()
+      settings.club_name  # => "My Club"
+
+      # Update club name
+      {:ok, updated} = Mv.Membership.update_settings(settings, %{club_name: "New Name"})
+  """
+  use Ash.Resource,
+    domain: Mv.Membership,
+    data_layer: AshPostgres.DataLayer
+
+  postgres do
+    table "settings"
+    repo Mv.Repo
+  end
+
+  resource do
+    description "Global application settings (singleton resource)"
+  end
+
+  actions do
+    defaults [:read]
+
+    # Internal create action - not exposed via code interface
+    # Used only as fallback in get_settings/0 if settings don't exist
+    # Settings should normally be created via seed script
+    create :create do
+      accept [:club_name]
+    end
+
+    update :update do
+      primary? true
+      accept [:club_name]
+    end
+  end
+
+  attributes do
+    uuid_primary_key :id
+
+    attribute :club_name, :string,
+      allow_nil?: false,
+      public?: true,
+      description: "The name of the association/club",
+      constraints: [
+        trim?: true,
+        min_length: 1
+      ]
+
+    timestamps()
+  end
+
+  validations do
+    validate present(:club_name), on: [:create, :update]
+    validate string_length(:club_name, min: 1), on: [:create, :update]
+  end
+end