Get user that created a message ruby on rails mongoid - ruby-on-rails

Question

I'm trying a query to get the user that created a message in a specific sala but I can't find the way.
I've got the query to get the messages of the specific sala, but I can't get the user that created the message.
Mensajes_controller (where I get the messages from the sala)
def index
#mensaje = #sala.mensajes.desc('_id').limit(20)
render json: #mensaje
end
set_sala (to get the room from which I want the messages)
def set_sala
if params[:sala_id]
#sala = Sala.find(params[:sala_id])
end
end
mensaje model
class Mensaje
include Mongoid::Document
include Mongoid::Timestamps::Created
field :cuerpo, type: String
validates :cuerpo, presence: true
belongs_to :user, foreign_key: :user_id
belongs_to :sala, foreign_key: :sala_id
end
user model
class User
include Mongoid::Document
include ActiveModel::SecurePassword
has_secure_password
field :password_digest, type: String
field :email, type: String
field :nombre, type: String
has_many :salas
has_many :mensajes
validates :nombre, presence: true
validates :email, presence: true
validates :password_digest, presence: true
end
Updating - Gemfile
source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }
ruby '2.5.5'
# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.2.3'
# Use Puma as the app server
gem 'puma', '~> 3.11'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
gem 'redis', '~> 4.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.12'
gem 'bcrypt', '~> 3.1.7'
gem 'mongoid-bcrypt-ruby'
gem 'devise'
gem 'kaminari-mongoid'
gem 'mongo'
# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development
gem 'mongoid', '~> 7.0.5'
# Reduces boot times through caching; required in config/boot.rb
gem 'bootsnap', '>= 1.1.0', require: false
# Use Rack CORS for handling Cross-Origin Resource Sharing (CORS), making cross-origin AJAX possible
gem 'rack-cors'
gem 'jwt_sessions', '~> 2.3'
gem 'mongoid-rspec', github: 'mongoid/mongoid-rspec', ref: '68c95b133be1a1482fe882e39afd33262147d1f4'
group :development, :test do
# Call 'byebug' anywhere in the code to stop execution and get a debugger console
gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
gem 'pry-rails'
gem 'rspec-rails'
gem 'factory_bot_rails'
gem 'shoulda-matchers'
end
group :development do
gem 'listen', '>= 3.0.5', '< 3.2'
# Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
gem 'spring'
gem 'spring-watcher-listen', '~> 2.0.0'
end
# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
Feel free to ask anything you may need. Thanks!

Answer 1

What about this?
#mensaje.user
and install kaminari-mongoid and maybe mongo gem.