resources: Add key to reources.GetRemote options map

If set, `key` will be used as the only cache key element for the resource.

The default behaviour is to calculate the key based on the URL and all the options.

This means that you can now do:

```
{{ $cacheKey := print $url (now.Format "2006-01-02") }}
{{ $resource := resource.GetRemote $url (dict "key" $cacheKey) }}
```

Fixes #9755

content/en/hugo-pipes/introduction.md

@@ -53,6 +53,19 @@ With `resources.GetRemote`, the first argument is a remote URL:
 
 `resources.Get` and `resources.GetRemote` return `nil` if the resource is not found.
 
+### Caching
+
+By default, Hugo calculates a cache key based on the `URL` and the `options` (e.g. headers) given.
+
+
+{{< new-in "0.97.0" >}} You can override this by setting a `key` in the options map. This can be used to get more fine grained control over how often a remote resource is fetched, e.g.:
+
+
+```go-html-template
+{{ $cacheKey := print $url (now.Format "2006-01-02") }}
+{{ $resource := resource.GetRemote $url (dict "key" $cacheKey) }}
+```
+
 ### Error Handling
 
 {{< new-in "0.91.0" >}}