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

lib/membership_fees/membership_fee_cycle.ex

@@ -0,0 +1,99 @@
+defmodule Mv.MembershipFees.MembershipFeeCycle do
+  @moduledoc """
+  Ash resource representing an individual membership fee cycle for a member.
+
+  ## Overview
+  MembershipFeeCycle represents a single billing cycle for a member. Each cycle
+  tracks the payment status and amount for a specific time period.
+
+  ## Attributes
+  - `cycle_start` - Start date of the billing cycle (aligned to calendar boundaries)
+  - `amount` - The fee amount for this cycle (stored for audit trail)
+  - `status` - Payment status: unpaid, paid, or suspended
+  - `notes` - Optional notes for this cycle
+
+  ## Design Decisions
+  - **No cycle_end field**: Calculated from cycle_start + interval (from fee type)
+  - **Amount stored per cycle**: Preserves historical amounts when fee type changes
+  - **Calendar-aligned cycles**: All cycles start on calendar boundaries
+
+  ## Relationships
+  - `belongs_to :member` - The member this cycle belongs to
+  - `belongs_to :membership_fee_type` - The fee type for this cycle
+
+  ## Constraints
+  - Unique constraint on (member_id, cycle_start) - one cycle per period per member
+  - CASCADE delete when member is deleted
+  - RESTRICT delete on membership_fee_type if cycles exist
+  """
+  use Ash.Resource,
+    domain: Mv.MembershipFees,
+    data_layer: AshPostgres.DataLayer
+
+  postgres do
+    table "membership_fee_cycles"
+    repo Mv.Repo
+  end
+
+  resource do
+    description "Individual membership fee cycle for a member"
+  end
+
+  actions do
+    defaults [:read, :destroy]
+
+    create :create do
+      primary? true
+      accept [:cycle_start, :amount, :status, :notes, :member_id, :membership_fee_type_id]
+    end
+
+    update :update do
+      primary? true
+      accept [:status, :notes]
+    end
+  end
+
+  attributes do
+    uuid_v7_primary_key :id
+
+    attribute :cycle_start, :date do
+      allow_nil? false
+      public? true
+      description "Start date of the billing cycle"
+    end
+
+    attribute :amount, :decimal do
+      allow_nil? false
+      public? true
+      description "Fee amount for this cycle (stored for audit trail)"
+    end
+
+    attribute :status, :atom do
+      allow_nil? false
+      public? true
+      default :unpaid
+      description "Payment status of this cycle"
+      constraints one_of: [:unpaid, :paid, :suspended]
+    end
+
+    attribute :notes, :string do
+      allow_nil? true
+      public? true
+      description "Optional notes for this cycle"
+    end
+  end
+
+  relationships do
+    belongs_to :member, Mv.Membership.Member do
+      allow_nil? false
+    end
+
+    belongs_to :membership_fee_type, Mv.MembershipFees.MembershipFeeType do
+      allow_nil? false
+    end
+  end
+
+  identities do
+    identity :unique_cycle_per_member, [:member_id, :cycle_start]
+  end
+end

lib/membership_fees/membership_fee_type.ex

@@ -0,0 +1,91 @@
+defmodule Mv.MembershipFees.MembershipFeeType do
+  @moduledoc """
+  Ash resource representing a membership fee type definition.
+
+  ## Overview
+  MembershipFeeType defines the different types of membership fees that can be
+  assigned to members. Each type has a fixed interval (billing cycle) and a
+  default amount.
+
+  ## Attributes
+  - `name` - Unique name for the fee type (e.g., "Standard", "Reduced", "Family")
+  - `amount` - The fee amount in the default currency (decimal)
+  - `interval` - Billing interval: monthly, quarterly, half_yearly, or yearly
+  - `description` - Optional description for the fee type
+
+  ## Immutability
+  The `interval` field is immutable after creation. This prevents complex
+  migration scenarios when changing billing cycles. To change intervals,
+  create a new fee type and migrate members.
+
+  ## Relationships
+  - `has_many :members` - Members assigned to this fee type
+  - `has_many :membership_fee_cycles` - All cycles using this fee type
+  """
+  use Ash.Resource,
+    domain: Mv.MembershipFees,
+    data_layer: AshPostgres.DataLayer
+
+  postgres do
+    table "membership_fee_types"
+    repo Mv.Repo
+  end
+
+  resource do
+    description "Membership fee type definition with interval and amount"
+  end
+
+  actions do
+    defaults [:read, :destroy]
+
+    create :create do
+      primary? true
+      accept [:name, :amount, :interval, :description]
+    end
+
+    update :update do
+      primary? true
+      # Note: interval is NOT in accept list - it's immutable after creation
+      # Immutability validation will be added in a future issue
+      accept [:name, :amount, :description]
+    end
+  end
+
+  attributes do
+    uuid_v7_primary_key :id
+
+    attribute :name, :string do
+      allow_nil? false
+      public? true
+      description "Unique name for the membership fee type"
+    end
+
+    attribute :amount, :decimal do
+      allow_nil? false
+      public? true
+      description "Fee amount in default currency"
+    end
+
+    attribute :interval, :atom do
+      allow_nil? false
+      public? true
+      description "Billing interval (immutable after creation)"
+      constraints one_of: [:monthly, :quarterly, :half_yearly, :yearly]
+    end
+
+    attribute :description, :string do
+      allow_nil? true
+      public? true
+      description "Optional description for the fee type"
+    end
+  end
+
+  relationships do
+    has_many :membership_fee_cycles, Mv.MembershipFees.MembershipFeeCycle
+    has_many :members, Mv.Membership.Member
+  end
+
+  identities do
+    identity :unique_name, [:name]
+  end
+end

lib/membership_fees/membership_fees.ex

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+defmodule Mv.MembershipFees do
+  @moduledoc """
+  Ash Domain for membership fee management.
+
+  ## Resources
+  - `MembershipFeeType` - Defines membership fee types with intervals and amounts
+  - `MembershipFeeCycle` - Individual membership fee cycles per member
+
+  ## Overview
+  This domain handles the complete membership fee lifecycle including:
+  - Fee type definitions (monthly, quarterly, half-yearly, yearly)
+  - Individual fee cycles for each member
+  - Payment status tracking (unpaid, paid, suspended)
+
+  ## Architecture Decisions
+  - `interval` field on MembershipFeeType is immutable after creation
+  - `cycle_end` is calculated, not stored (from cycle_start + interval)
+  - `amount` is stored per cycle for audit trail when prices change
+  """
+  use Ash.Domain,
+    extensions: [AshAdmin.Domain, AshPhoenix]
+
+  admin do
+    show? true
+  end
+
+  resources do
+    resource Mv.MembershipFees.MembershipFeeType do
+      define :create_membership_fee_type, action: :create
+      define :list_membership_fee_types, action: :read
+      define :update_membership_fee_type, action: :update
+      define :destroy_membership_fee_type, action: :destroy
+    end
+
+    resource Mv.MembershipFees.MembershipFeeCycle do
+      define :create_membership_fee_cycle, action: :create
+      define :list_membership_fee_cycles, action: :read
+      define :update_membership_fee_cycle, action: :update
+      define :destroy_membership_fee_cycle, action: :destroy
+    end
+  end
+end