Explicitly disallow fetch() caching

For the sake of our customers, I don't feel it's worth us fighting that "this implementation is wrong" with our customers in the middle.

If this hack were specific to an implementation of fetch, I'd feel differently, but given this is in the spec, and we're just being overly explicit, rather than relying on a "default" behavior, I'm more ok with it.

I still firmly disagree with implementations that are choosing to cache POST, _especially_ also with an Authorization header, but there's only so much I/we can control.

See context: vercel/next.js#46856

Fixes: #101 #99

src/index.ts

@@ -40,6 +40,7 @@ type Req = {
   method: string
   headers: Record<string, string>
   body: string
+  cache?: string
 }
 
 type Res = {
@@ -265,7 +266,14 @@ async function postJSON<T>(config: Config, url: string | URL, body = {}): Promis
       'Content-Type': 'application/json',
       'User-Agent': `database-js/${Version}`,
       Authorization: `Basic ${auth}`
-    }
+    },
+    // XXX: this should be overly redundant and the default behavior should be sufficient,
+    // since we both are a POST request and send an Authorization header, this request should
+    // by all means be considered an "unsafe" request for caching purposes. But it seems some
+    // implementations think differently, so I don't see harm in being overly explicit, since
+    // this `cache` argument is a part of the actual Fetch API spec anyways. We're just opting
+    // out of the default behavior.
+    cache: 'no-store'
   })
 
   if (response.ok) {