Help with storing data on item

I’m very new to sponge but have been coding in java and using the Spigot API for 3 years.

I’m having trouble with storing data on an itemstack, I’m trying to store a String and a Double value (key and value)
In spigot, I would use NBT Tags but I’m not so sure about Sponge. The docs have a part on it but it’s been removed so I’m in the dark atm.

Any help would be greatly appreciated, Spoonfeeding is appreciated aswell :joy:

Thank you in advance.

The data storage api is changing massively in API 8 to something a bit more simple.

In API 7 its a bit confusing, so much so that a generator was created by pieflavor

I would just use that