How to use custom tables & Attachment API in ServiceNow

When ServiceNow has custom tables in use and attachments needs to be sent through, default sys_id mapping cannot be used. Target URI is usually the import set table, but another, usually a default entity, is created in ServiceNow. Following modification is required for the attachments.upload.attachment.uri system configuration:

It is described in ServiceNow adapter as follows by default:

"/api/now/attachment/file?table_name=${message:entityType}&table_sys_id=${sys_id}&file_name=${fileName}"

Placeholders for entity type and sys_id needs to be replaced with the targeted entity type (if hard-coded) or an outbound attribute from rule mappings e.g.:

"/api/now/attachment/file?table_name=${u_task_type}&table_sys_id=${u_sys_id}&file_name=${fileName}"

Please note that conversation attributes cannot be referred to in system configuration.