feat: generic Userinfo and Introspect functions (#389)

BREAKING CHANGE: rp.Userinfo and rs.Introspect now require
a type parameter.

pkg/client/rp/userinfo_example_test.go

@@ -0,0 +1,45 @@
+package rp_test
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/zitadel/oidc/v3/pkg/client/rp"
+	"github.com/zitadel/oidc/v3/pkg/oidc"
+)
+
+type UserInfo struct {
+	Subject string `json:"sub,omitempty"`
+	oidc.UserInfoProfile
+	oidc.UserInfoEmail
+	oidc.UserInfoPhone
+	Address *oidc.UserInfoAddress `json:"address,omitempty"`
+
+	// Foo and Bar are custom claims
+	Foo string `json:"foo,omitempty"`
+	Bar struct {
+		Val1 string `json:"val_1,omitempty"`
+		Val2 string `json:"val_2,omitempty"`
+	} `json:"bar,omitempty"`
+
+	// Claims are all the combined claims, including custom.
+	Claims map[string]any `json:"-,omitempty"`
+}
+
+func (u *UserInfo) GetSubject() string {
+	return u.Subject
+}
+
+func ExampleUserinfo_custom() {
+	rpo, err := rp.NewRelyingPartyOIDC(context.TODO(), "http://localhost:8080", "clientid", "clientsecret", "http://example.com/redirect", []string{oidc.ScopeOpenID, oidc.ScopeProfile, oidc.ScopeEmail, oidc.ScopePhone})
+	if err != nil {
+		panic(err)
+	}
+
+	info, err := rp.Userinfo[*UserInfo](context.TODO(), "accesstokenstring", "Bearer", "userid", rpo)
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(info)
+}