feat: join request backend

priv/repo/migrations/20260220120000_add_join_requests.exs

@@ -0,0 +1,42 @@
+defmodule Mv.Repo.Migrations.AddJoinRequests do
+  @moduledoc """
+  Adds join_requests table for public join flow (onboarding concept §2.3.2).
+  """
+  use Ecto.Migration
+
+  def up do
+    create table(:join_requests, primary_key: false) do
+      add :id, :uuid, null: false, default: fragment("uuid_generate_v7()"), primary_key: true
+      add :email, :string, null: false
+      add :confirmation_token_hash, :string, null: false
+      add :status, :string, null: false
+      add :submitted_at, :utc_datetime_usec, null: false
+      add :source, :string, null: false
+      add :schema_version, :bigint, null: false
+      add :payload, :map, null: true
+      add :approved_at, :utc_datetime_usec, null: true
+      add :rejected_at, :utc_datetime_usec, null: true
+      add :reviewed_by_user_id, :uuid, null: true
+
+      add :inserted_at, :utc_datetime_usec,
+        null: false,
+        default: fragment("(now() AT TIME ZONE 'utc')")
+
+      add :updated_at, :utc_datetime_usec,
+        null: false,
+        default: fragment("(now() AT TIME ZONE 'utc')")
+    end
+
+    create unique_index(:join_requests, [:confirmation_token_hash],
+             name: "join_requests_unique_confirmation_token_hash_index"
+           )
+  end
+
+  def down do
+    drop_if_exists unique_index(:join_requests, [:confirmation_token_hash],
+                  name: "join_requests_unique_confirmation_token_hash_index"
+                )
+
+    drop table(:join_requests)
+  end
+end