fixed bugfix where another user could not store the same object again

fixed the primary keys => all the classes have now composite primary key which contais an id + user_id, necessary gem: 'composite_primary_keys'
fixed the user_id relation => every class now "belongs_to" user

pls kill me know

Gemfile

@@ -37,6 +37,9 @@ gem 'devise-encryptable', '0.2.0'
 # Reduces boot times through caching; required in config/boot.rb
 gem 'bootsnap', '>= 1.4.2', require: false
 
+# for composite primary keys
+gem 'composite_primary_keys'
+
 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]