chore: Add support for message_templates in API inbox (#4835)

app/models/channel/api.rb

@@ -2,14 +2,15 @@
 #
 # Table name: channel_api
 #
-#  id             :bigint           not null, primary key
-#  hmac_mandatory :boolean          default(FALSE)
-#  hmac_token     :string
-#  identifier     :string
-#  webhook_url    :string
-#  created_at     :datetime         not null
-#  updated_at     :datetime         not null
-#  account_id     :integer          not null
+#  id                    :bigint           not null, primary key
+#  additional_attributes :jsonb
+#  hmac_mandatory        :boolean          default(FALSE)
+#  hmac_token            :string
+#  identifier            :string
+#  webhook_url           :string
+#  created_at            :datetime         not null
+#  updated_at            :datetime         not null
+#  account_id            :integer          not null
 #
 # Indexes
 #
@@ -21,7 +22,7 @@ class Channel::Api < ApplicationRecord
   include Channelable
 
   self.table_name = 'channel_api'
-  EDITABLE_ATTRS = [:webhook_url].freeze
+  EDITABLE_ATTRS = [:webhook_url, { additional_attributes: {} }].freeze
 
   has_secure_token :identifier
   has_secure_token :hmac_token