feat: APIs to assign agents_bots as assignee in conversations (#12836)

## Summary
- add an assignee_agent_bot_id column as an initital step to prototype
this before fully switching to polymorphic assignee
- update assignment APIs and conversation list / show endpoints to
reflect assignee as agent bot
- ensure webhook payloads contains agent bot assignee


[Codex
Task](https://chatgpt.com/codex/tasks/task_e_6912833377e48326b6641b9eee32d50f)

---------

Co-authored-by: Pranav <pranav@chatwoot.com>

app/models/agent_bot.rb

@@ -21,9 +21,18 @@ class AgentBot < ApplicationRecord
   include AccessTokenable
   include Avatarable
 
+  scope :accessible_to, lambda { |account|
+    account_id = account&.id
+    where(account_id: [nil, account_id])
+  }
+
   has_many :agent_bot_inboxes, dependent: :destroy_async
   has_many :inboxes, through: :agent_bot_inboxes
   has_many :messages, as: :sender, dependent: :nullify
+  has_many :assigned_conversations, class_name: 'Conversation',
+                                    foreign_key: :assignee_agent_bot_id,
+                                    dependent: :nullify,
+                                    inverse_of: :assignee_agent_bot
   belongs_to :account, optional: true
   enum bot_type: { webhook: 0 }
 

app/models/conversation.rb

@@ -20,6 +20,7 @@
 #  created_at             :datetime         not null
 #  updated_at             :datetime         not null
 #  account_id             :integer          not null
+#  assignee_agent_bot_id  :bigint
 #  assignee_id            :integer
 #  campaign_id            :bigint
 #  contact_id             :bigint
@@ -65,6 +66,7 @@ class Conversation < ApplicationRecord
   validates :inbox_id, presence: true
   validates :contact_id, presence: true
   before_validation :validate_additional_attributes
+  before_validation :reset_agent_bot_when_assignee_present
   validates :additional_attributes, jsonb_attributes_length: true
   validates :custom_attributes, jsonb_attributes_length: true
   validates :uuid, uniqueness: true
@@ -98,6 +100,7 @@ class Conversation < ApplicationRecord
   belongs_to :account
   belongs_to :inbox
   belongs_to :assignee, class_name: 'User', optional: true, inverse_of: :assigned_conversations
+  belongs_to :assignee_agent_bot, class_name: 'AgentBot', optional: true
   belongs_to :contact
   belongs_to :contact_inbox
   belongs_to :team, optional: true
@@ -180,6 +183,18 @@ class Conversation < ApplicationRecord
     true
   end
 
+  # Virtual attribute till we switch completely to polymorphic assignee
+  def assignee_type
+    return 'AgentBot' if assignee_agent_bot_id.present?
+    return 'User' if assignee_id.present?
+
+    nil
+  end
+
+  def assigned_entity
+    assignee_agent_bot || assignee
+  end
+
   def tweet?
     inbox.inbox_type == 'Twitter' && additional_attributes['type'] == 'tweet'
   end
@@ -226,6 +241,12 @@ class Conversation < ApplicationRecord
     self.additional_attributes = {} unless additional_attributes.is_a?(Hash)
   end
 
+  def reset_agent_bot_when_assignee_present
+    return if assignee_id.blank?
+
+    self.assignee_agent_bot_id = nil
+  end
+
   def determine_conversation_status
     self.status = :resolved and return if contact.blocked?
 
@@ -251,8 +272,8 @@ class Conversation < ApplicationRecord
   end
 
   def list_of_keys
-    %w[team_id assignee_id status snoozed_until custom_attributes label_list waiting_since first_reply_created_at
-       priority]
+    %w[team_id assignee_id assignee_agent_bot_id status snoozed_until custom_attributes label_list waiting_since
+       first_reply_created_at priority]
   end
 
   def allowed_keys?