Fix duplicate invites (#1437)

Co-authored-by: Josh Pigford <josh@joshpigford.com>

app/models/invitation.rb

@@ -5,6 +5,7 @@ class Invitation < ApplicationRecord
   validates :email, presence: true, format: { with: URI::MailTo::EMAIL_REGEXP }
   validates :role, presence: true, inclusion: { in: %w[admin member] }
   validates :token, presence: true, uniqueness: true
+  validates_uniqueness_of :email, scope: :family_id, message: "has already been invited to this family"
   validate :inviter_is_admin
 
   before_validation :generate_token, on: :create

db/migrate/20241108150422_add_unique_email_index_to_invitations.rb

@@ -0,0 +1,5 @@
+class AddUniqueEmailIndexToInvitations < ActiveRecord::Migration[7.2]
+  def change
+    add_index :invitations, [ :email, :family_id ], unique: true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2024_10_30_222235) do
+ActiveRecord::Schema[7.2].define(version: 2024_11_08_150422) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -427,6 +427,7 @@ ActiveRecord::Schema[7.2].define(version: 2024_10_30_222235) do
     t.datetime "expires_at"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["email", "family_id"], name: "index_invitations_on_email_and_family_id", unique: true
     t.index ["email"], name: "index_invitations_on_email"
     t.index ["family_id"], name: "index_invitations_on_family_id"
     t.index ["inviter_id"], name: "index_invitations_on_inviter_id"