Create a new entitlement registration line

Creates a new entitlement registration line with an optional file attachment.

Attachment Rules:

• Whether an attachment is required or not allowed is determined by the entitlement configuration.
• entitlements API can be used to fetch the entitlement configuration, which includes whether an attachment is required or not allowed for a specific entitlement.
• If an attachment is required but not provided, the request will be rejected with a 400 error.
• If an attachment is provided when not configured in entitlement, the document will still be stored
• Supported file types for attachments are PDF, PNG and JPEG. If the provided file is not one of these types, the request will be rejected with a 400 error.