web/client: update synology token from /api/auth call

When the /api/auth response indicates that synology auth is needed,
fetch the SynoToken and store it for future API calls.  This doesn't yet
update the server-side code to set the new SynoAuth field.

Updates tailscale/corp#14335

Signed-off-by: Will Norris <will@tailscale.com>

client/web/src/api.ts

@@ -1,4 +1,5 @@
 let csrfToken: string
+let synoToken: string | undefined // required for synology API requests
 let unraidCsrfToken: string | undefined // required for unraid POST requests (#8062)
 
 // apiFetch wraps the standard JS fetch function with csrf header
@@ -15,9 +16,13 @@ export function apiFetch(
 ): Promise<Response> {
   const urlParams = new URLSearchParams(window.location.search)
   const nextParams = new URLSearchParams(params)
-  const token = urlParams.get("SynoToken")
-  if (token) {
-    nextParams.set("SynoToken", token)
+  if (synoToken) {
+    nextParams.set("SynoToken", synoToken)
+  } else {
+    const token = urlParams.get("SynoToken")
+    if (token) {
+      nextParams.set("SynoToken", token)
+    }
   }
   const search = nextParams.toString()
   const url = `api${endpoint}${search ? `?${search}` : ""}`
@@ -62,6 +67,10 @@ function updateCsrfToken(r: Response) {
   }
 }
 
+export function setSynoToken(token?: string) {
+  synoToken = token
+}
+
 export function setUnraidCsrfToken(token?: string) {
   unraidCsrfToken = token
 }