feat: track oauth new-user result

backend/src/main/java/com/openisle/controller/InviteController.java

@@ -0,0 +1,23 @@
+package com.openisle.controller;
+
+import com.openisle.service.InviteService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.security.core.Authentication;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.Map;
+
+@RestController
+@RequestMapping("/api/invite")
+@RequiredArgsConstructor
+public class InviteController {
+    private final InviteService inviteService;
+
+    @PostMapping("/generate")
+    public Map<String, String> generate(Authentication auth) {
+        String token = inviteService.generate(auth.getName());
+        return Map.of("token", token);
+    }
+}