feat: make oauth access tokens RFC 9068 compliant

backend/internal/service/custom_claim_service.go

@@ -39,6 +39,7 @@ func isReservedClaim(key string) bool {
 		"acr",
 		"amr",
 		"azp",
+		"client_id",
 		"nbf",
 		"jti":
 		return true

backend/internal/service/e2etest_service.go

@@ -864,7 +864,7 @@ func (s *TestService) SignAccessToken(ctx context.Context, userID, clientID stri
 	keyGetter := func(context.Context) (interface{}, error) {
 		return oidc.SigningKeyFromSigner(s.jwtService)
 	}
-	strategy := compose.NewOAuth2JWTStrategy(keyGetter, coreStrategy, fositeConfig)
+	strategy := oidc.NewAccessTokenStrategy(compose.NewOAuth2RFC9068JWTStrategy(keyGetter, coreStrategy, fositeConfig), common.EnvConfig.AppURL)
 
 	expiresAt := time.Now().UTC().Add(AccessTokenDuration)
 	if expired {