[Bug]: 0.20.27, 0.20.28, 0.20.29 clients cannot create/update gateways with 0.21.0 server

[jvstme]

Steps to reproduce

$ dstack --version
0.20.27

$ cat test.dstack.yml
type: gateway
backend: aws
region: eu-north-1
domain: example.com

$ dstack apply -f test.dstack.yml
Server validation error: 
{'detail': [{'input': None,
             'loc': ['body', 'spec', 'configuration', 'router'],
             'msg': 'Extra inputs are not permitted',
             'type': 'extra_forbidden'}]}

Actual behaviour

No response

Expected behaviour

No response

dstack version

0.21.0

Server logs

Additional information

No response