Help choosing the right solenoid valve for espresso machine project

Hi all,
beginner here and have gone through a few basic projects, making led's blink, buttons, etc.
Mainly to learn enough for the actual project I want to do, which is adding a flow-profiling modification to an espresso machine.
The electronics portion can be described as simply arduino control of a solenoid valve.

I've spent a couple days trying to find the right solenoid for the project but there are so many options and am getting lost. I also want to choose one that is as arduino-friendly as possible.

From what I read, I will need an NPN transistor and diode if the solenoid needs more than a 5v signal (which seems likely at this point) so maybe I won't need to necessarily worry about iarduino-friendliness.

I need to find a direct acting, food-safe, stainless steel or brass, normally open, 2-way valve that can handle water pressure from 0-15bar.
is there a favorite store with hobbyist-friendly sales people?

PS Sometimes I see people using a transistor for controlling a higher voltage application and sometimes I see people just use a separate relay. Since this is an On/Off application, it really shouldn't matter which way I go, right?

I need to find a direct acting, food-safe, stainless steel or brass, normally open, 2-way valve that can handle water pressure from 0-15bar.

Are you sure it needs to be normally open?

Water will come out if you loose power.

This will be between the pump and boiler, so no external outlet.