Fix frozen string Ruby 3.4 warnings.

app/helpers/dynamic_errors_helper.rb

@@ -46,7 +46,7 @@ def error_messages_for(*params)
           end
         end.join.html_safe
 
-        contents = ''
+        contents = +''
         contents << content_tag(options[:header_tag] || :h2, header_message) unless header_message.blank?
         contents << content_tag(:p, message) unless message.blank?
         contents << content_tag(:ul, error_messages)

app/helpers/rubygems_helper.rb

@@ -127,11 +127,11 @@ def rubygem_security_events_link(rubygem)
   end
 
   def links_to_owners(rubygem)
-    rubygem.owners.sort_by(&:id).inject("") { |link, owner| link << link_to_user(owner) }.html_safe
+    rubygem.owners.sort_by(&:id).inject(+"") { |link, owner| link << link_to_user(owner) }.html_safe
   end
 
   def links_to_owners_without_mfa(rubygem)
-    rubygem.owners.without_mfa.sort_by(&:id).inject("") { |link, owner| link << link_to_user(owner) }.html_safe
+    rubygem.owners.without_mfa.sort_by(&:id).inject(+"") { |link, owner| link << link_to_user(owner) }.html_safe
   end
 
   def link_to_user(user)

test/functional/api/v1/api_keys_controller_test.rb

@@ -210,7 +210,7 @@ def self.should_expect_otp_for_update
     context "with credentials with invalid encoding" do
       setup do
         @user = create(:user)
-        authorize_with("\x12\xff\x12:creds".force_encoding(Encoding::UTF_8))
+        authorize_with(String.new("\x12\xff\x12:creds", encoding: Encoding::UTF_8))
         get :show
       end
       should_deny_access

test/models/user_test.rb

@@ -981,20 +981,20 @@ class UserTest < ActiveSupport::TestCase
 
     should "preserve valid characters so that the format error can be returned" do
       # UTF-8 "香" character, which is valid UTF-8, but we reject utf-8 in email addresses
-      assert_equal "香@example.com", User.normalize_email("\[email protected]".force_encoding("utf-8"))
+      assert_equal "香@example.com", User.normalize_email(String.new("\[email protected]", encoding: "utf-8"))
 
       # ISO-8859-1 "Å" character (valid in ISO-8859-1)
-      encoded_email = "myem\[email protected]".force_encoding("ISO-8859-1")
+      encoded_email = String.new("myem\[email protected]", encoding: "ISO-8859-1")
 
       assert_equal encoded_email, User.normalize_email(encoded_email)
     end
 
     should "return an empty string on invalid inputs" do
       # bad encoding when sent as ASCII-8BIT
-      assert_equal "", User.normalize_email("\[email protected]".force_encoding("ascii"))
+      assert_equal "", User.normalize_email(String.new("\[email protected]", encoding: "ascii"))
 
       # ISO-8859-1 "Å" character (invalid in UTF-8, which uses \xC385 for this character)
-      assert_equal "", User.normalize_email("myem\[email protected]".force_encoding("UTF-8"))
+      assert_equal "", User.normalize_email(String.new("myem\[email protected]", encoding: "UTF-8"))
     end
 
     should "return an empty string for nil" do