feat: Added auth functionality and added additional documentation

Gemfile.lock

README.md

...generators/nexus_cqrs/templates/register_cqrs_handlers.rb

lib/nexus_cqrs.rb

lib/nexus_cqrs/auth/auth.rb

lib/nexus_cqrs/auth/ownable.rb

lib/nexus_cqrs/auth/permission_provider.rb

lib/nexus_cqrs/auth/user_context.rb

lib/nexus_cqrs/base_command.rb

lib/nexus_cqrs/base_command_handler.rb

lib/nexus_cqrs/base_message.rb

lib/nexus_cqrs/base_middleware.rb

lib/nexus_cqrs/base_query.rb

lib/nexus_cqrs/base_query_handler.rb

lib/nexus_cqrs/command_bus.rb

lib/nexus_cqrs/command_executor.rb

lib/nexus_cqrs/helpers.rb

lib/nexus_cqrs/version.rb

nexus_cqrs.gemspec

spec/lib/base_message_spec.rb