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/...`

pkg/client/rp/cli/cli.go

@@ -13,13 +13,13 @@ const (
 	loginPath = "/login"
 )
 
-func CodeFlow(ctx context.Context, relyingParty rp.RelyingParty, callbackPath, port string, stateProvider func() string) *oidc.Tokens {
+func CodeFlow[C oidc.IDClaims](ctx context.Context, relyingParty rp.RelyingParty, callbackPath, port string, stateProvider func() string) *oidc.Tokens[C] {
 	codeflowCtx, codeflowCancel := context.WithCancel(ctx)
 	defer codeflowCancel()
 
-	tokenChan := make(chan *oidc.Tokens, 1)
+	tokenChan := make(chan *oidc.Tokens[C], 1)
 
-	callback := func(w http.ResponseWriter, r *http.Request, tokens *oidc.Tokens, state string, rp rp.RelyingParty) {
+	callback := func(w http.ResponseWriter, r *http.Request, tokens *oidc.Tokens[C], state string, rp rp.RelyingParty) {
 		tokenChan <- tokens
 		msg := "<p><strong>Success!</strong></p>"
 		msg = msg + "<p>You are authenticated and can now return to the CLI.</p>"