Require MFA for gem pushes

This adds the `rubygems_mfa_required` metadata to the gemspec,
requiring multi-factor authentication for privileged operations
on RubyGems.org.

This is a protection against supply chain attacks like the recent
NPM Axios compromise: https://socket.dev/blog/axios-npm-package-compromised

Reference: https://guides.rubygems.org/mfa-requirement-opt-in/

Author: neilvcarvalho

factory_bot_rails.gemspec

@@ -13,7 +13,10 @@ Gem::Specification.new do |s|
                   "factory_bot and Rails 6.1 or newer"
 
   s.files = Dir["lib/**/*"] + %w[CONTRIBUTING.md LICENSE NEWS.md README.md]
-  s.metadata["changelog_uri"] = "https://github.com/thoughtbot/factory_bot_rails/blob/main/NEWS.md"
+  s.metadata = {
+    "changelog_uri" = "https://github.com/thoughtbot/factory_bot_rails/blob/main/NEWS.md",
+    "rubygems_mfa_required" => "true"
+  }
   s.require_paths = ["lib"]
   s.required_ruby_version = Gem::Requirement.new(">= 3.1.0")
   s.executables = []