[18.0] endpoint: fix lambda

[ivantodorovich]

Backport from the 19.0 migration

[OCA-git-bot]

Hi @simahawk,
some modules you are maintaining are being modified, check this out!

[ivantodorovich]

⚠️ The CI is failing due to an unrelated issue:

2026-05-19 18:58:02,544 316 ERROR odoo odoo.addons.endpoint.tests.test_endpoint: FAIL: TestEndpoint.test_unlink
Traceback (most recent call last):
  File "/opt/odoo-venv/bin/coverage", line 6, in <module>
    sys.exit(main())
  File "/opt/odoo-venv/lib/python3.10/site-packages/coverage/cmdline.py", line 1164, in main
    status = CoverageScript().command_line(argv)
  File "/opt/odoo-venv/lib/python3.10/site-packages/coverage/cmdline.py", line 853, in command_line
    return self.do_run(options, args)
  File "/opt/odoo-venv/lib/python3.10/site-packages/coverage/cmdline.py", line 1043, in do_run
    runner.run()
  File "/opt/odoo-venv/lib/python3.10/site-packages/coverage/execfile.py", line 213, in run
    exec(code, main_mod.__dict__)
  File "/opt/odoo-venv/bin/odoo", line 8, in <module>
    odoo.cli.main()
  File "/opt/odoo/odoo/cli/command.py", line 76, in main
    o.run(args)
  File "/opt/odoo/odoo/cli/server.py", line 182, in run
    main(args)
  File "/opt/odoo/odoo/cli/server.py", line 175, in main
    rc = odoo.service.server.start(preload=preload, stop=stop)
  File "/opt/odoo/odoo/service/server.py", line 1462, in start
    rc = server.run(preload, stop)
  File "/opt/odoo/odoo/service/server.py", line 627, in run
    rc = preload_registries(preload)
  File "/opt/odoo/odoo/service/server.py", line 1393, in preload_registries
    result = loader.run_suite(post_install_suite, global_report=registry._assertion_report)
  File "/opt/odoo/odoo/tests/loader.py", line 118, in run_suite
    suite(results)
AssertionError: Found unexpected attributes on endpoint.endpoint: _endpoint_route_prefix

[yostashiro]

LGTM.