refactor: extract helper modules to remove code duplication

lib/mv/membership/helpers/visibility_config.ex

@@ -0,0 +1,55 @@
+defmodule Mv.Membership.Helpers.VisibilityConfig do
+  @moduledoc """
+  Helper functions for normalizing member field visibility configuration.
+
+  Handles conversion between string keys (from JSONB) and atom keys (Elixir convention).
+  JSONB in PostgreSQL converts atom keys to string keys when storing.
+  This module provides functions to normalize these back to atoms for Elixir usage.
+  """
+
+  @doc """
+  Normalizes visibility config map keys from strings to atoms.
+
+  JSONB in PostgreSQL converts atom keys to string keys when storing.
+  This function converts them back to atoms for Elixir usage.
+
+  ## Parameters
+
+    - `config` - A map with either string or atom keys
+
+  ## Returns
+
+    A map with atom keys (where possible)
+
+  ## Examples
+
+      iex> normalize(%{"first_name" => true, "email" => false})
+      %{first_name: true, email: false}
+
+      iex> normalize(%{first_name: true, email: false})
+      %{first_name: true, email: false}
+
+      iex> normalize(%{"invalid_field" => true})
+      %{}
+  """
+  @spec normalize(map()) :: map()
+  def normalize(config) when is_map(config) do
+    Enum.reduce(config, %{}, fn
+      {key, value}, acc when is_atom(key) ->
+        Map.put(acc, key, value)
+
+      {key, value}, acc when is_binary(key) ->
+        try do
+          atom_key = String.to_existing_atom(key)
+          Map.put(acc, atom_key, value)
+        rescue
+          ArgumentError -> acc
+        end
+
+      _, acc ->
+        acc
+    end)
+  end
+
+  def normalize(_), do: %{}
+end