FEATURE: Custom unsubscribe options (#17090)

With this change, plugins can create custom unsubscribe keys, extend the unsubscribe view with custom preferences, and decide how they are updated.

lib/email_controller_helper/topic_email_unsubscriber.rb

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+module EmailControllerHelper
+  class TopicEmailUnsubscriber < BaseEmailUnsubscriber
+    def prepare_unsubscribe_options(controller)
+      super(controller)
+      watching = TopicUser.notification_levels[:watching]
+
+      topic = unsubscribe_key.associated_topic
+
+      controller.instance_variable_set(:@topic, topic)
+      controller.instance_variable_set(
+        :@watching_topic,
+        TopicUser.exists?(user: key_owner, notification_level: watching, topic_id: topic.id)
+      )
+
+      return if topic.category_id.blank?
+      return if !CategoryUser.exists?(user: key_owner, notification_level: CategoryUser.watching_levels, category_id: topic.category_id)
+
+      controller.instance_variable_set(
+        :@watched_count,
+        TopicUser.joins(:topic)
+          .where(user: key_owner, notification_level: watching).where(topics: { category_id: topic.category_id }).count
+      )
+    end
+
+    def unsubscribe(params)
+      updated = super(params)
+
+      topic = unsubscribe_key.associated_topic
+      return updated if topic.nil?
+
+      if params[:unwatch_topic]
+        TopicUser.where(topic_id: topic.id, user_id: key_owner.id)
+          .update_all(notification_level: TopicUser.notification_levels[:tracking])
+
+        updated = true
+      end
+
+      if params[:unwatch_category] && topic.category_id
+        TopicUser.joins(:topic)
+          .where(user: key_owner, notification_level: TopicUser.notification_levels[:watching])
+          .where(topics: { category_id: topic.category_id })
+          .update_all(notification_level: TopicUser.notification_levels[:tracking])
+
+        CategoryUser
+          .where(user_id: key_owner.id, category_id: topic.category_id, notification_level: CategoryUser.watching_levels)
+          .destroy_all
+
+        updated = true
+      end
+
+      if params[:mute_topic]
+        TopicUser.where(topic_id: topic.id, user_id: key_owner.id).update_all(notification_level: TopicUser.notification_levels[:muted])
+
+        updated = true
+      end
+
+      updated
+    end
+  end
+end