feat: prevent deleted email conversations from syncing again (#14612)

# Pull Request Template

## Description

Prevent deleted email conversations from being synced into Chatwoot
again while they are still within the IMAP sync window.

When an admin explicitly deletes an email conversation, the incoming
email message IDs are stored temporarily in Redis. IMAP sync checks
these recently deleted message IDs in addition to existing message
records. Each Redis key expires automatically after two days.

This applies only to explicit conversation deletion. Individual message
deletion, inbox deletion, and account deletion keep their existing
behavior.

Fixes
[CW-7214](https://linear.app/chatwoot/issue/CW-7214/deleted-mails-in-gmail-inbox-gets-synced-again)

app/controllers/api/v1/accounts/conversations_controller.rb

@@ -140,7 +140,7 @@ class Api::V1::Accounts::ConversationsController < Api::V1::Accounts::BaseContro
 
   def destroy
     authorize @conversation, :destroy?
-    ::DeleteObjectJob.perform_later(@conversation, Current.user, request.ip)
+    ::Conversations::DeleteService.new(conversation: @conversation, user: Current.user, ip: request.ip).perform
     head :ok
   end
 

app/services/conversations/delete_service.rb

@@ -0,0 +1,16 @@
+class Conversations::DeleteService
+  pattr_initialize [:conversation!, :user, :ip]
+
+  def perform
+    track_deleted_email_messages
+    ::DeleteObjectJob.perform_later(conversation, user, ip)
+  end
+
+  private
+
+  def track_deleted_email_messages
+    return unless conversation.inbox.email?
+
+    Imap::DeletedMessageTracker.new(inbox: conversation.inbox).record(conversation.messages.incoming.pluck(:source_id))
+  end
+end

app/services/imap/base_fetch_email_service.rb

@@ -38,7 +38,11 @@ class Imap::BaseFetchEmailService
   end
 
   def email_already_present?(channel, message_id)
-    channel.inbox.messages.find_by(source_id: message_id).present?
+    channel.inbox.messages.find_by(source_id: message_id).present? || deleted_message_tracker.deleted?(message_id)
+  end
+
+  def deleted_message_tracker
+    @deleted_message_tracker ||= Imap::DeletedMessageTracker.new(inbox: channel.inbox)
   end
 
   def fetch_mail_for_channel

app/services/imap/deleted_message_tracker.rb

@@ -0,0 +1,28 @@
+require 'digest'
+
+class Imap::DeletedMessageTracker
+  TTL = 2.days.to_i
+
+  pattr_initialize [:inbox!]
+
+  def record(source_ids)
+    return unless inbox.email?
+
+    keys = source_ids.compact_blank.map { |source_id| redis_key(source_id) }
+    return if keys.blank?
+
+    Redis::Alfred.pipelined do |pipeline|
+      keys.each { |key| pipeline.set(key, true, ex: TTL) }
+    end
+  end
+
+  def deleted?(source_id)
+    Redis::Alfred.exists?(redis_key(source_id))
+  end
+
+  private
+
+  def redis_key(source_id)
+    format(Redis::RedisKeys::IMAP_DELETED_MESSAGE, inbox_id: inbox.id, message_id_digest: Digest::SHA256.hexdigest(source_id))
+  end
+end