deduplicate users as well

app/controllers/users_controller.rb

@@ -168,11 +168,12 @@ class UsersController < ApplicationController
 
     require 'csv'
 
-    CSV.parse(users_csv, :headers => true) do |row|
+    users = CSV.parse(users_csv, :headers => true).map { |row|
       fields = row.to_hash
       fields[:room_id] = room_id
-      User.create!(fields)
-    end
+      fields
+    }
+    User.upsert_all(users, unique_by: [:room_id, :email])
 
     respond_to do |format|
       format.html { redirect_to room_users_url(room_id), notice: 'Users were successfully created.' }

app/models/user.rb

@@ -6,4 +6,7 @@ class User < ApplicationRecord
   attribute :invited, :boolean, default: false
   attribute :vote, :boolean, default: true
   attribute :proxy, :boolean, default: false
+
+  validates :email, uniqueness: { scope: :room_id }
+  validates :room_id, uniqueness: { scope: :email }
 end

db/migrate/20230127133700_upsertable_users.rb

@@ -0,0 +1,8 @@
+class UpsertableUsers < ActiveRecord::Migration[6.0]
+    def change
+        change_column_default :users, :created_at, from: nil, to: ->{ 'now()' }
+        change_column_default :users, :updated_at, from: nil, to: ->{ 'now()' }
+        add_index :users, [:room_id, :email], unique: true
+    end
+  end
+