Add Templated LINE notification message API and custom aggregation units for PNP

[github-actions]

line/line-openapi#131

This adds the Templated LINE notification message (PNP) API and enables custom aggregation units (CAU) for LINE notification messages.

Changes

Templated LINE notification message (PNP)

• Add POST /v2/bot/message/pnp/templated/push to send a notification message built from a pre-registered template (templateKey + body with emphasizedItem / items / buttons).
• Add GET /v2/bot/message/delivery/pnp/templated to get the number of sent templated notification messages (reuses NumberOfMessagesResponse).
• Add schemas: PnpTemplatedMessageRequest, PnpTemplatedMessageBody, PnpTemplatedEmphasizedItem, PnpTemplatedItem, PnpTemplatedButton.

Custom aggregation units (CAU) for PNP

• Add customAggregationUnits to the flexible PNP request (PnpMessagesRequest) and to the new templated PNP request, so their delivery can be aggregated per unit via the existing unit-based statistics APIs.

References

• Templated notification message: https://developers.line.biz/en/docs/partner-docs/line-notification-messages/template/
• Notification message statistics: https://developers.line.biz/en/docs/partner-docs/line-notification-messages/statistics/