Add opt-in built-in Feishu OIDC issuer for OpenVPN

backend/internal/service/openvpn/oidc.go

@@ -14,6 +14,7 @@ import (
 	"syscall"
 	"time"
 
+	"vpn-platform/backend/internal/identityprovider"
 	"vpn-platform/backend/internal/model"
 	"vpn-platform/backend/internal/service"
 	"vpn-platform/backend/internal/store"
@@ -103,6 +104,9 @@ func prepareOIDC(t *model.Tunnel, cfg map[string]interface{}) error {
 	if service.Str(cfg, "oidc_client_secret") == "" {
 		cfg["oidc_client_secret"] = old["oidc_client_secret"]
 	}
+	if secret, ok := identityprovider.ClientForIssuer(service.Str(cfg, "oidc_issuer"), service.Str(cfg, "oidc_client_id")); ok {
+		cfg["oidc_client_secret"] = secret
+	}
 	if service.Str(cfg, "oidc_client_secret") == "" {
 		return fmt.Errorf("oidc_client_secret 必填；请从 OIDC 发行者对应的客户端凭据中复制 Client Secret")
 	}