Remove multi_json and replace with StdLib JSON

Fix: #213

Author: otherguy

activerecord-session_store.gemspec

@@ -23,7 +23,6 @@ Gem::Specification.new do |s|
   s.add_dependency('actionpack', '>= 6.1')
   s.add_dependency('railties', '>= 6.1')
   s.add_dependency('rack', '>= 2.0.8', '< 4')
-  s.add_dependency('multi_json', '~> 1.11', '>= 1.11.2')
   s.add_dependency('cgi', '>= 0.3.6')
 
   s.add_development_dependency('sqlite3')

lib/active_record/session_store.rb

@@ -2,7 +2,7 @@
 require 'active_record/session_store/version'
 require 'action_dispatch/session/active_record_store'
 require 'active_support/core_ext/hash/keys'
-require 'multi_json'
+require 'json'
 
 module ActiveRecord
   module SessionStore
@@ -62,12 +62,12 @@ def self.dump(value)
       # Uses built-in JSON library to encode/decode session
       class JsonSerializer
         def self.load(value)
-          hash = MultiJson.load(value)
+          hash = JSON.parse(value)
           hash.is_a?(Hash) ? hash.with_indifferent_access[:value] : hash
         end
 
         def self.dump(value)
-          MultiJson.dump(value: value)
+          JSON.dump(value: value)
         end
       end