feat (ee): APIs to configure an auto assignment limit for inboxes (#4672)

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

enterprise/app/controllers/enterprise/api/v1/accounts/inboxes_controller.rb

@@ -0,0 +1,9 @@
+module Enterprise::Api::V1::Accounts::InboxesController
+  def inbox_attributes
+    super + ee_inbox_attributes
+  end
+
+  def ee_inbox_attributes
+    [auto_assignment_config: [:max_assignment_limit]]
+  end
+end

enterprise/app/models/enterprise/inbox.rb

@@ -0,0 +1,20 @@
+module Enterprise::Inbox
+  def member_ids_with_assignment_capacity
+    max_assignment_limit = auto_assignment_config['max_assignment_limit']
+    overloaded_agent_ids = max_assignment_limit.present? ? get_agent_ids_over_assignment_limit(max_assignment_limit) : []
+    super - overloaded_agent_ids
+  end
+
+  private
+
+  def get_agent_ids_over_assignment_limit(limit)
+    conversations.open.select(:assignee_id).group(:assignee_id).having("count(*) >= #{limit.to_i}").filter_map(&:assignee_id)
+  end
+
+  def ensure_valid_max_assignment_limit
+    return if auto_assignment_config['max_assignment_limit'].blank?
+    return if auto_assignment_config['max_assignment_limit'].to_i.positive?
+
+    errors.add(:auto_assignment_config, 'max_assignment_limit must be greater than 0')
+  end
+end