Custom Authentication with Nakama

I want to have a custom authentication proccess - not via Facebook, Google, Steam etc. Is that possible?

A custom identifier can be used in a similar way to a device identifier to login or register a user. This option should be used if you have an external or custom user identity service which you want to use. For example EA’s Origin service handles accounts which have their own user IDs.

A custom identifier must contain alphanumeric characters with dashes and be between 10 and 60 bytes.

You can choose a custom username when creating the account. To do this, set username to a custom name. If you want to only authenticate without implicitly creating a user account, set create to false.

Lear more about custom authentication here https://heroiclabs.com/docs/authentication/#custom