Is Medium give any Sub-Domain ?

[sharos]

I am an airdrop/bounty hunter and local community manager. Recently i see a project which have subdomain from Medium.

I am talking about this one: https://seseral-finance.medium.com

I am not Medium expert.
I want to know, How to they got this sub-domain?  They have any partnership with medium? Or Medium give subdomain to everyone? Have any prossge to get subdomain?