allow for custom domain in k8s-nameserver #11

Job	Run time
race-root-integration (1/4)	11m 14s
test (amd64, -coverprofile=/tmp/coverage.out)	7m 9s
windows	4m 15s
race-root-integration (2/4)	1m 21s
test (amd64, -race, 1/3)	7m 41s
race-root-integration (3/4)	1m 14s
test (amd64, -race, 2/3)	7m 38s
race-root-integration (4/4)	1m 15s
test (amd64, -race, 3/3)	6m 32s
android	55s
test (386)	5m 15s
cross (linux, arm64)	3m 54s
crossmin (plan9, amd64)	47s
depaware	30s
cross (linux, 386)	3m 51s
crossmin (aix, ppc64)	55s
cross (linux, loong64)	3m 44s
fuzz	7m 12s
cross (linux, arm, 5)	3m 44s
go_generate	1m 6s
cross (linux, arm, 7)	5m 1s
cross (darwin, amd64)	3m 43s
go_mod_tidy	26s
ios	48s
cross (darwin, arm64)	3m 47s
licenses	5s
cross (windows, amd64)	3m 30s
privileged	54s
race-build	4m 29s
cross (windows, arm64)	3m 35s
cross (freebsd, amd64)	3m 35s
tailscale_go	29s
vm	0s
cross (openbsd, amd64)	3m 39s
wasm	7m 40s
staticcheck (linux, amd64)	3m 36s
staticcheck (windows, amd64)	3m 35s
staticcheck (darwin, amd64)	3m 34s
staticcheck (windows, 386)	3m 27s
check_mergeability	2s
notify_slack	1s
	2h 16m 8s

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