MONGOID-4833 MONGOID-4849 Ruby 3.0 compatibility for 7.0 branch (#4771)

* MONGOID-4833 Avoid delegate warning message on ruby MRI 2.7.x

`
..lib/mongoid.rb:104: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
../.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/activesupport-5.2.4.2/lib/active_support/core_ext/module/delegation.rb:154: warning: The called method `delegate' is defined here
`

* MONGOID-4849 test ActiveSupport delegation (backported from #4739)

Co-authored-by: Oleg Pudeyev <oleg@bsdpower.com>

Co-authored-by: Alexander Oryol <eagle.alex@gmail.com>
Co-authored-by: Oleg Pudeyev <oleg@bsdpower.com>

lib/mongoid.rb

@@ -102,5 +102,5 @@ def client(name)
   #   Mongoid.database = Mongo::Connection.new.db("test")
   #
   # @since 1.0.0
-  delegate(*(Config.public_instance_methods(false) - [ :logger=, :logger ] << { to: Config }))
+  delegate(*(Config.public_instance_methods(false) - [ :logger=, :logger ]), to: Config)
 end

spec/app/models/delegating_patient.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+# encoding: utf-8
+
+class DelegatingPatient
+  include Mongoid::Document
+
+  embeds_one :email
+
+  # Instance level delegation
+  delegate :address, to: :email
+
+  class << self
+    # Class level delegation
+    delegate :default_client, to: ::Mongoid
+  end
+end

spec/integration/document_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+# encoding: utf-8
+
+require 'spec_helper'
+
+describe Mongoid::Document do
+  context 'when including class uses delegate' do
+    let(:patient) do
+      DelegatingPatient.new(
+        email: Email.new(address: 'test@example.com'),
+      )
+    end
+
+    it 'works for instance level delegation' do
+      patient.address.should == 'test@example.com'
+    end
+
+    it 'works for class level delegation' do
+      DelegatingPatient.default_client.should be Mongoid.default_client
+    end
+  end
+end