Serialized SD-JWTs without keybinding do not match spec

[romano21A]

I'm using this library to generate SD-JWTs without keybinding (sometimes called format for issuance in the code). According to the spec, they should always end with a ~ after the last disclosure.

This is not the case when calling Serialize() on SelectiveDisclosureJWT. This should be a simple fix here:

vc-go/sdjwt/common/common.go

Line 84 in 778f9e3

func (cf *CombinedFormatForIssuance) Serialize() string {