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/integration_test.go

@@ -235,19 +235,19 @@ func RunAuthorizationCodeFlow(t *testing.T, opServer *httptest.Server, clientID,
 	}
 
 	var email string
-	redirect := func(w http.ResponseWriter, r *http.Request, tokens *oidc.Tokens, state string, rp rp.RelyingParty, info oidc.UserInfo) {
+	redirect := func(w http.ResponseWriter, r *http.Request, tokens *oidc.Tokens[*oidc.IDTokenClaims], state string, rp rp.RelyingParty, info *oidc.UserInfo) {
 		require.NotNil(t, tokens, "tokens")
 		require.NotNil(t, info, "info")
 		t.Log("access token", tokens.AccessToken)
 		t.Log("refresh token", tokens.RefreshToken)
 		t.Log("id token", tokens.IDToken)
-		t.Log("email", info.GetEmail())
+		t.Log("email", info.Email)
 
 		accessToken = tokens.AccessToken
 		refreshToken = tokens.RefreshToken
 		idToken = tokens.IDToken
-		email = info.GetEmail()
-		http.Redirect(w, r, targetURL, http.StatusFound)
+		email = info.Email
+		http.Redirect(w, r, targetURL, 302)
 	}
 	rp.CodeExchangeHandler(rp.UserinfoCallback(redirect), provider)(capturedW, get)
 
@@ -258,7 +258,6 @@ func RunAuthorizationCodeFlow(t *testing.T, opServer *httptest.Server, clientID,
 		}
 	}()
 	require.Less(t, capturedW.Code, 400, "token exchange response code")
-	require.Less(t, capturedW.Code, 400, "token exchange response code")
 
 	//nolint:bodyclose
 	resp = capturedW.Result()