Change GuildPrivateThreadCreate to have NonInvitable field instead of Invitable

[myrkvi]

The current implementation has the field Invitable and the JSON annotation omitempty, which results in the field being omitted when it is false. Not explicitly setting an invitable state should result in it being invitable, and as such, having NonInvitable achieves this.

[topi314]

I'd rather have this be a pointer instead to be consistent with other fields & the discord docs

[myrkvi]

I'd rather have this be a pointer instead to be consistent with other fields & the discord docs

Definitely a saner way to do it :sweat_smile:

[topi314]

sane is arguable in this case, getting pointers from primitives is annoying after all lol

[topi314]

thanks