Add support for sending ready line

[MaxThom]

Hi,

thanks for your library and awesome db! I generate line protocol entry via reflection and I got all my lines ready to be pushed. I want to use the library so it handles batch, connection, tls, etc. Is there a way where I can write the line directly to the buffer?

[puzpuzpuz]

Is there a way where I can write the line directly to the buffer?

Currently, the senders don't expose this in their public API. That's because public methods include table/column name and value validation.