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

pkg/oidc/verifier.go

@@ -32,6 +32,12 @@ type ClaimsSignature interface {
 	SetSignatureAlgorithm(algorithm jose.SignatureAlgorithm)
 }
 
+type IDClaims interface {
+	Claims
+	GetSignatureAlgorithm() jose.SignatureAlgorithm
+	GetAccessTokenHash() string
+}
+
 var (
 	ErrParse                   = errors.New("parsing of request failed")
 	ErrIssuerInvalid           = errors.New("issuer does not match")