GetClaim() returning interface is awkward to use. Use output parameter instead?

[arianvp]

Is your feature request related to a problem? Please describe.

The following code is awkward as I need to guess that the structure that GetClaim() returns is map[string]string.

		val, ok := introspectionResponse.GetClaim("cnf").(map[string]string)
		if !ok {
			http.Error(rw, "", http.StatusUnauthorized)
			return
		}

		expectedClientCertificateHash, err := base64.URLEncoding.DecodeString(val["x5t#S256"])
		if err != nil {
			http.Error(rw, "", http.StatusUnauthorized)
			return
		}
		if !bytes.Equal(clientCertificateHash[:], expectedClientCertificateHash) {
			http.Error(rw, "", http.StatusUnauthorized)
			return
		}

Describe the solution you'd like

I'd prefer GetClaim() to take an output parameter instead. so that I can marshal safely to my own struct type:

func (r IntrospectionResponse) GetClaim(key string, out interface{}) error {...}

type ConfirmationClaim struct {
        CertificateThumbprint string `json:"x5t#S256"`
}

var cnf ConfirmationClaim
err := introspectionResponse.GetClaim("cnf", &cnf)
if err != nil { ... }
expectedClientCertificateHash, err := base64.URLEncoding.DecodeString(cnf.CertificateThumbprint)
if err != nil { ... }
if !bytes.Equal(clientCertificateHash[:], cnf.CertificateThumbprint {
	http.Error(rw, "", http.StatusUnauthorized)
	return
}

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[fforootd]

Hi @arianvp - I agree that this can be improved 😁

Currently all hands are in the version 2 prepwork for ZITADEL, so it might take 2-4 weeks before someone can get a hold of this issue. Hope thats not too bad for you.

[arianvp]

No rush. The code works as is. It's just awkward.

[muhlemmer]

#283 should improve this. If you have any other feedback, please let us know