How to ignore subscription when create topic?

[xiaofan-luan]

In our use cases, we can not unsubscribe on crash cases.
This will cause serious issue because backlog will be full and no further produce works.
In fact we maintained our own checkpoint in stream and keep the data in pulsar for certain period so backlog is not really helpful for us, is there a way to claim skip the backlog when create a collection? we want data to be expired in 2 days after it is written