DEV: Add user modifier to prevent updating ip_address (#28280)

app/models/user.rb

@@ -1038,6 +1038,10 @@ class User < ActiveRecord::Base
   end
 
   def self.update_ip_address!(user_id, new_ip:, old_ip:)
+    can_update_ip_address =
+      DiscoursePluginRegistry.apply_modifier(:user_can_update_ip_address, user_id: user_id)
+    return if !can_update_ip_address
+
     unless old_ip == new_ip || new_ip.blank?
       DB.exec(<<~SQL, user_id: user_id, ip_address: new_ip)
         UPDATE users

spec/models/user_spec.rb

@@ -3165,6 +3165,11 @@ RSpec.describe User do
   end
 
   describe "#update_ip_address!" do
+    let!(:plugin) { Plugin::Instance.new }
+    let!(:modifier) { :user_can_update_ip_address }
+    let!(:deny_block) { Proc.new { false } }
+    let!(:allow_block) { Proc.new { true } }
+
     it "updates ip_address correctly" do
       expect do user.update_ip_address!("127.0.0.1") end.to change {
         user.reload.ip_address.to_s
@@ -3173,6 +3178,19 @@ RSpec.describe User do
       expect do user.update_ip_address!("127.0.0.1") end.to_not change { user.reload.ip_address }
     end
 
+    it "allows plugins to control updating ip_address" do
+      DiscoursePluginRegistry.register_modifier(plugin, modifier, &deny_block)
+      expect do user.update_ip_address!("127.0.0.1") end.to_not change { user.reload.ip_address }
+
+      DiscoursePluginRegistry.register_modifier(plugin, modifier, &allow_block)
+      expect do user.update_ip_address!("127.0.0.1") end.to change {
+        user.reload.ip_address.to_s
+      }.to("127.0.0.1")
+    ensure
+      DiscoursePluginRegistry.unregister_modifier(plugin, modifier, &deny_block)
+      DiscoursePluginRegistry.unregister_modifier(plugin, modifier, &allow_block)
+    end
+
     describe "keeping old ip address" do
       before { SiteSetting.keep_old_ip_address_count = 2 }