tailcfg: define a type for NodeCapability

Instead of untyped string, add a type to identify these.

Updates #cleanup

Signed-off-by: Maisem Ali <maisem@tailscale.com>

envknob/logknob/logknob.go

@@ -9,6 +9,7 @@ import (
 	"sync/atomic"
 
 	"tailscale.com/envknob"
+	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/views"
 )
@@ -22,7 +23,7 @@ import (
 // c2n log level changes), and via capabilities from a NetMap (so users can
 // enable logging via the ACL JSON).
 type LogKnob struct {
-	capName string
+	capName tailcfg.NodeCapability
 	cap     atomic.Bool
 	env     func() bool
 	manual  atomic.Bool
@@ -30,7 +31,7 @@ type LogKnob struct {
 
 // NewLogKnob creates a new LogKnob, with the provided environment variable
 // name and/or NetMap capability.
-func NewLogKnob(env, cap string) *LogKnob {
+func NewLogKnob(env string, cap tailcfg.NodeCapability) *LogKnob {
 	if env == "" && cap == "" {
 		panic("must provide either an environment variable or capability")
 	}
@@ -58,7 +59,7 @@ func (lk *LogKnob) Set(v bool) {
 // about; we use this rather than a concrete type to avoid a circular
 // dependency.
 type NetMap interface {
-	SelfCapabilities() views.Slice[string]
+	SelfCapabilities() views.Slice[tailcfg.NodeCapability]
 }
 
 // UpdateFromNetMap will enable logging if the SelfNode in the provided NetMap

envknob/logknob/logknob_test.go

@@ -64,7 +64,7 @@ func TestLogKnob(t *testing.T) {
 
 		testKnob.UpdateFromNetMap(&netmap.NetworkMap{
 			SelfNode: (&tailcfg.Node{
-				Capabilities: []string{
+				Capabilities: []tailcfg.NodeCapability{
 					"https://tailscale.com/cap/testing",
 				},
 			}).View(),