feat(membership-fees): add database schema and Ash domain structure

lib/membership/member.ex

@@ -79,7 +79,8 @@ defmodule Mv.Membership.Member do
       # user_id is NOT in accept list to prevent direct foreign key manipulation
       argument :user, :map, allow_nil?: true
 
-      accept @member_fields
+      # Accept member fields plus membership_fee_type_id (belongs_to FK)
+      accept @member_fields ++ [:membership_fee_type_id]
 
       change manage_relationship(:custom_field_values, type: :create)
 
@@ -112,7 +113,8 @@ defmodule Mv.Membership.Member do
       # user_id is NOT in accept list to prevent direct foreign key manipulation
       argument :user, :map, allow_nil?: true
 
-      accept @member_fields
+      # Accept member fields plus membership_fee_type_id (belongs_to FK)
+      accept @member_fields ++ [:membership_fee_type_id]
 
       change manage_relationship(:custom_field_values, on_match: :update, on_no_match: :create)
 
@@ -394,6 +396,15 @@ defmodule Mv.Membership.Member do
       writable?: false,
       public?: false,
       select_by_default?: false
+
+    # Membership fee fields
+    # membership_fee_start_date: Date from which membership fees should be calculated
+    # If nil, calculated from join_date + global setting
+    attribute :membership_fee_start_date, :date do
+      allow_nil? true
+      public? true
+      description "Date from which membership fees should be calculated"
+    end
   end
 
   relationships do
@@ -402,6 +413,16 @@ defmodule Mv.Membership.Member do
     # This references the User's member_id attribute
     # The relationship is optional (allow_nil? true by default)
     has_one :user, Mv.Accounts.User
+
+    # Membership fee relationships
+    # belongs_to: The fee type assigned to this member
+    # Optional for MVP - can be nil if no fee type assigned yet
+    belongs_to :membership_fee_type, Mv.MembershipFees.MembershipFeeType do
+      allow_nil? true
+    end
+
+    # has_many: All fee cycles for this member
+    has_many :membership_fee_cycles, Mv.MembershipFees.MembershipFeeCycle
   end
 
   # Define identities for upsert operations