chore(vpn): upsert agents with their network status (coder#15659)

Closes coder#14734.
- Each outgoing agent upsertion also includes the timestamp of the last wireguard handshake.
- Agent upsertions will be created, for existing agents, with an updated last handshake time on a regular, fixed, interval of 10 seconds.

Author: ethanndickson

.golangci.yaml

@@ -175,8 +175,6 @@ linters-settings:
       - name: modifies-value-receiver
       - name: package-comments
       - name: range
-      - name: range-val-address
-      - name: range-val-in-closure
       - name: receiver-naming
       - name: redefines-builtin-id
       - name: string-of-int
@@ -199,6 +197,10 @@ linters-settings:
   govet:
     disable:
       - loopclosure
+  gosec:
+    excludes:
+      # Implicit memory aliasing of items from a range statement (irrelevant as of Go v1.22)
+      - G601
 
 issues:
   # Rules listed here: https://github.com/securego/gosec#available-rules
@@ -238,7 +240,6 @@ linters:
     - errname
     - errorlint
     - exhaustruct
-    - exportloopref
     - forcetypeassert
     - gocritic
     # gocyclo is may be useful in the future when we start caring

vpn/client.go

@@ -11,6 +11,7 @@ import (
 	"tailscale.com/net/dns"
 	"tailscale.com/wgengine/router"
 
+	"github.com/google/uuid"
 	"github.com/tailscale/wireguard-go/tun"
 
 	"cdr.dev/slog"
@@ -23,6 +24,7 @@ import (
 
 type Conn interface {
 	CurrentWorkspaceState() (tailnet.WorkspaceUpdate, error)
+	GetPeerDiagnostics(peerID uuid.UUID) tailnet.PeerDiagnostics
 	Close() error
 }