feat: Add APIs to manage custom roles in Chatwoot (#9995)

Co-authored-by: Pranav <pranavrajs@gmail.com>

db/migrate/20240726220747_add_custom_roles.rb

@@ -0,0 +1,16 @@
+class AddCustomRoles < ActiveRecord::Migration[7.0]
+  def change
+    # Create the roles table
+    create_table :custom_roles do |t|
+      t.string :name
+      t.string :description
+      t.references :account, null: false
+      t.text :permissions, array: true, default: []
+      t.timestamps
+    end
+
+    # Associate the custom role with account user
+    # Add the custom_role_id column to the account_users table
+    add_reference :account_users, :custom_role, optional: true
+  end
+end