Frontend+API: Namen ändern (POST /user/rename)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

endpoints_test.go

@@ -221,6 +221,52 @@ func TestVoteRequiresAuthAndValidMode(t *testing.T) {
 	}
 }
 
+func TestRenameUser(t *testing.T) {
+	srv := newTestServer(t)
+	alice := registerAndLogin(t, srv, "alice")
+	registerAndLogin(t, srv, "bob")
+
+	// Zu kurz -> 400.
+	resp := postForm(t, alice, srv.URL+"/user/rename", url.Values{"user": {"ab"}})
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusBadRequest {
+		t.Fatalf("zu kurz: erwartet 400, bekam %d", resp.StatusCode)
+	}
+
+	// Bereits vergeben -> 409.
+	resp = postForm(t, alice, srv.URL+"/user/rename", url.Values{"user": {"bob"}})
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusConflict {
+		t.Fatalf("vergeben: erwartet 409, bekam %d", resp.StatusCode)
+	}
+
+	// Gültig -> 200 + neuer Name.
+	resp = postForm(t, alice, srv.URL+"/user/rename", url.Values{"user": {"alice2"}})
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("rename: erwartet 200, bekam %d", resp.StatusCode)
+	}
+	var out struct {
+		Username string `json:"username"`
+	}
+	json.NewDecoder(resp.Body).Decode(&out)
+	if out.Username != "alice2" {
+		t.Fatalf("erwarteter Name alice2, bekam %q", out.Username)
+	}
+
+	// Profil unter dem neuen Namen erreichbar, alter Name weg.
+	r2, _ := http.Get(srv.URL + "/u/alice2/info")
+	r2.Body.Close()
+	if r2.StatusCode != http.StatusOK {
+		t.Fatalf("/u/alice2/info: erwartet 200, bekam %d", r2.StatusCode)
+	}
+	r3, _ := http.Get(srv.URL + "/u/alice/info")
+	r3.Body.Close()
+	if r3.StatusCode != http.StatusNotFound {
+		t.Fatalf("/u/alice/info: erwartet 404, bekam %d", r3.StatusCode)
+	}
+}
+
 func TestDeleteUser(t *testing.T) {
 	srv := newTestServer(t)
 	alice := registerAndLogin(t, srv, "alice")