client: update DNSConfig type (tailscale#8916)

This PR adds DNSFilterURL to the DNSConfig type to be used by
control changes to add DNS filtering logic

Fixes #cleanup

Signed-off-by: Richard Castro <richard@tailscale.com>

Author: rscastro

client/tailscale/apitype/controltype.go

@@ -10,6 +10,7 @@ type DNSConfig struct {
 	Domains           []string                 `json:"domains"`
 	Nameservers       []string                 `json:"nameservers"`
 	Proxied           bool                     `json:"proxied"`
+	DNSFilterURL      string                   `json:"DNSFilterURL"`
 }
 
 type DNSResolver struct {

tailcfg/tailcfg.go

@@ -1403,6 +1403,8 @@ type DNSConfig struct {
 	//
 	// Matches are case insensitive.
 	ExitNodeFilteredSet []string `json:",omitempty"`
+	// DNSFilterURL contains a user inputed URL that should have a list of domains to be blocked
+	DNSFilterURL string `json:",omitempty"`
 }
 
 // DNSRecord is an extra DNS record to add to MagicDNS.