feat: member user relation

lib/accounts/user.ex

@@ -60,15 +60,54 @@ defmodule Mv.Accounts.User do
   end
 
   actions do
-    defaults [:read, :create, :destroy, :update]
+    defaults [:read, :create, :destroy]
+
+    update :update do
+      primary? true
+      require_atomic? false
+    end
 
     create :create_user do
+      # Only accept email directly - member_id is NOT in accept list
+      # This prevents direct foreign key manipulation, forcing use of manage_relationship
       accept [:email]
+      # Allow member to be passed as argument for relationship management
+      argument :member, :map, allow_nil?: true
       upsert? true
+
+      # Manage the member relationship during user creation
+      change manage_relationship(:member, :member,
+               # Look up existing member and relate to it
+               on_lookup: :relate,
+               # Error if member doesn't exist in database
+               on_no_match: :error,
+               # If member already linked to this user, ignore (shouldn't happen in create)
+               on_match: :ignore,
+               # If no member provided, that's fine (optional relationship)
+               on_missing: :ignore
+             )
     end
 
     update :update_user do
+      # Only accept email directly - member_id is NOT in accept list
+      # This prevents direct foreign key manipulation, forcing use of manage_relationship
       accept [:email]
+      # Allow member to be passed as argument for relationship management
+      argument :member, :map, allow_nil?: true
+      # Required because custom validation function cannot be done atomically
+      require_atomic? false
+
+      # Manage the member relationship during user update
+      change manage_relationship(:member, :member,
+               # Look up existing member and relate to it
+               on_lookup: :relate,
+               # Error if member doesn't exist in database
+               on_no_match: :error,
+               # If same member provided, that's fine (allows updates with same member)
+               on_match: :ignore,
+               # If no member provided, remove existing relationship (allows member removal)
+               on_missing: :unrelate
+             )
     end
 
     # Admin action for direct password changes in admin panel
@@ -76,6 +115,7 @@ defmodule Mv.Accounts.User do
     update :admin_set_password do
       accept [:email]
       argument :password, :string, allow_nil?: false, sensitive?: true
+      require_atomic? false
 
       # Set the strategy context that HashPasswordChange expects
       change set_context(%{strategy_name: :password})
@@ -125,6 +165,28 @@ defmodule Mv.Accounts.User do
     validate string_length(:password, min: 8) do
       where action_is([:register_with_password, :admin_set_password])
     end
+
+    # Prevent overwriting existing member relationship
+    # This validation ensures race condition safety by requiring explicit two-step process:
+    # 1. Remove existing member (set member to nil)
+    # 2. Add new member
+    # This prevents accidental overwrites when multiple admins work simultaneously
+    validate fn changeset, _context ->
+      member_arg = Ash.Changeset.get_argument(changeset, :member)
+      current_member_id = changeset.data.member_id
+
+      # Only trigger if:
+      # - member argument is provided AND has an ID
+      # - user currently has a member
+      # - the new member ID is different from current member ID
+      if member_arg && member_arg[:id] && current_member_id &&
+           member_arg[:id] != current_member_id do
+        {:error,
+         field: :member, message: "User already has a member. Remove existing member first."}
+      else
+        :ok
+      end
+    end
   end
 
   def validate_oidc_id_present(changeset, _context) do
@@ -146,12 +208,16 @@ defmodule Mv.Accounts.User do
   end
 
   relationships do
+    # 1:1 relationship - User can optionally belong to one Member
+    # This automatically creates a `member_id` attribute in the User table
+    # The relationship is optional (allow_nil? true by default)
     belongs_to :member, Mv.Membership.Member
   end
 
   identities do
     identity :unique_email, [:email]
     identity :unique_oidc_id, [:oidc_id]
+    identity :unique_member, [:member_id]
   end
 
   # You can customize this if you wish, but this is a safe default that