Add user generator that accepts arguments (faker-ruby#1671)

  The new user class method will now allow you to do this

  ```
  user = Faker::Internet.user('name', 'email', password')
  => {'name' => 'John Doe', 'email' => 'fake_email@test.com', 'password' => 'pass123' }
  ```

doc/default/internet.md

@@ -1,6 +1,10 @@
 # Faker::Internet
 
 ```ruby
+# Keyword arguments: name, username, email, password, domain_name, user_agent, uuid etc... 
+Faker::Internet.user #=> { username: 'alexie', email: 'alexie@example.net' }
+Faker::Internet.user('username', 'email', 'password') #=> { username: 'alexie', email: 'alexie@example.net', password: 'DtEf9P8wS31iMyC' }
+
 # Keyword arguments: name, separators
 Faker::Internet.email #=> "eliza@mann.net"
 Faker::Internet.email(name: 'Nancy') #=> "nancy@terry.biz"

lib/faker/default/internet.rb

@@ -277,6 +277,13 @@ def uuid
         '%08x-%04x-%04x-%04x-%04x%08x' % ary # rubocop:disable Style/FormatString
       end
 
+      def user(*args)
+        user_hash = {}
+        args = %w[username email] if args.empty?
+        args.each { |arg| user_hash[:"#{arg}"] = send(arg) }
+        user_hash
+      end
+
       alias user_name username
     end
   end

test/faker/default/test_faker_internet.rb

@@ -295,4 +295,23 @@ def test_uuid
     assert_equal(36, uuid.size)
     assert_match(/\A\h{8}-\h{4}-4\h{3}-\h{4}-\h{12}\z/, uuid)
   end
+
+  def test_user_with_args
+    user = @tester.user('username', 'email', 'password')
+    assert user[:username].match(/[a-z]+((_|\.)[a-z]+)?/)
+    assert user[:email].match(/.+@.+\.\w+/)
+    assert user[:password].match(/\w{3}/)
+  end
+
+  def test_user_without_args
+    user = @tester.user
+    assert user[:username].match(/[a-z]+((_|\.)[a-z]+)?/)
+    assert user[:email].match(/.+@.+\.\w+/)
+  end
+
+  def test_user_with_invalid_args
+    assert_raises NoMethodError do
+      @tester.user('xyx')
+    end
+  end
 end