Given a travel related situation, and given a specific question about the situation, summarize the question into a title
Q: I'm aware there's a form you can sign if ground staff at an airport doesn't want to let you to board an aircraft due to ignorance regarding the destination's entry (or in this case transit) requirements. This way, the carrier's liability is waived if you don't get into your destination.

What is the form called? In other words, what exactly should I ask for?

More likely than not, I'm going to have to ask for this at Tbilisi airport, from where I'm taking a flight to Doha in 3 days (in transit to London). As I only hold an ID card, which is accepted for the UK (my destination), I don't expect to get an easy time boarding the Tbilisi-Doha flight (even though I'll not be entering Qatar), because Timatic doesn't explicitly state that I can transit Qatar on my ID (nor does it state the opposite). Hence, such a form would be of great help.

I've read about this in this blog, where the author, who had trouble boarding a flight to Minsk for transit with her Portuguese ID card, writes:

I wrote some haiku style poems on my phone until the airline man came with a sheet for me to sign: 'It's to make you responsible for coming back, in case they don't allow you to stay in Minsk or enter Georgia.'

A:
What form waives the airline's liability in case of an entry refusal?