feat: generic Userinfo and Introspect functions (#389)

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

pkg/client/rs/introspect_example_test.go

@@ -0,0 +1,52 @@
+package rs_test
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/zitadel/oidc/v3/pkg/client/rs"
+	"github.com/zitadel/oidc/v3/pkg/oidc"
+)
+
+type IntrospectionResponse struct {
+	Active     bool                     `json:"active"`
+	Scope      oidc.SpaceDelimitedArray `json:"scope,omitempty"`
+	ClientID   string                   `json:"client_id,omitempty"`
+	TokenType  string                   `json:"token_type,omitempty"`
+	Expiration oidc.Time                `json:"exp,omitempty"`
+	IssuedAt   oidc.Time                `json:"iat,omitempty"`
+	NotBefore  oidc.Time                `json:"nbf,omitempty"`
+	Subject    string                   `json:"sub,omitempty"`
+	Audience   oidc.Audience            `json:"aud,omitempty"`
+	Issuer     string                   `json:"iss,omitempty"`
+	JWTID      string                   `json:"jti,omitempty"`
+	Username   string                   `json:"username,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 ExampleIntrospect_custom() {
+	rss, err := rs.NewResourceServerClientCredentials(context.TODO(), "http://localhost:8080", "clientid", "clientsecret")
+	if err != nil {
+		panic(err)
+	}
+
+	resp, err := rs.Introspect[*IntrospectionResponse](context.TODO(), rss, "accesstokenstring")
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(resp)
+}