refactor: use struct types for claim related types (#283)

* oidc: add regression tests for token claim json

this helps to verify that the same JSON is produced,
after these types are refactored.

* refactor: use struct types for claim related types

BREAKING CHANGE:
The following types are changed from interface to struct type:

- AccessTokenClaims
- IDTokenClaims
- IntrospectionResponse
- UserInfo and related types.

The following methods of OPStorage now take a pointer to a struct type,
instead of an interface:

- SetUserinfoFromScopes
- SetUserinfoFromToken
- SetIntrospectionFromToken

The following functions are now generic, so that type-safe extension
of Claims is now possible:

- op.VerifyIDTokenHint
- op.VerifyAccessToken
- rp.VerifyTokens
- rp.VerifyIDToken

- Changed UserInfoAddress to pointer in UserInfo and
IntrospectionResponse.
This was needed to make omitempty work correctly.
- Copy or merge maps in IntrospectionResponse and SetUserInfo

* op: add example for VerifyAccessToken

* fix: rp: wrong assignment in WithIssuedAtMaxAge

WithIssuedAtMaxAge assigned its value to v.maxAge, which was wrong.
This change fixes that by assiging the duration to v.maxAgeIAT.

* rp: add VerifyTokens example

* oidc: add standard references to:

- IDTokenClaims
- IntrospectionResponse
- UserInfo

* only count coverage for `./pkg/...`

example/client/github/github.go

@@ -13,6 +13,7 @@ import (
 	"github.com/zitadel/oidc/v2/pkg/client/rp"
 	"github.com/zitadel/oidc/v2/pkg/client/rp/cli"
 	"github.com/zitadel/oidc/v2/pkg/http"
+	"github.com/zitadel/oidc/v2/pkg/oidc"
 )
 
 var (
@@ -43,7 +44,7 @@ func main() {
 	state := func() string {
 		return uuid.New().String()
 	}
-	token := cli.CodeFlow(ctx, relyingParty, callbackPath, port, state)
+	token := cli.CodeFlow[*oidc.IDTokenClaims](ctx, relyingParty, callbackPath, port, state)
 
 	client := github.NewClient(relyingParty.OAuthConfig().Client(ctx, token.Token))