docs: remote recipes

docs/operators/handbook.md

@@ -480,3 +480,23 @@ abra app secret insert localhost ssl_cert v1 "$(cat localhost.crt)"
 abra app secret insert localhost ssl_key v1 "$(cat localhost.key)"
 ```
 4. Re-deploy `traefik` with `--force` and voila!
+
+## Remote recipes
+
+!!! warning "This is only available in the currently unreleased version of `abra`"
+
+    Please see [this issue](https://git.coopcloud.tech/coop-cloud/organising/issues/583) to track current progress towards a release. All feedback and testing are welcome on this new feature. The design is not finalised yet.
+
+It is possible to specify a remote recipe in your `.env` file:
+
+```
+RECIPE=mygit.org/myorg/cool-recipe.git:1.3.12
+```
+
+Where `1.3.12` is an optional pinned version. When `abra` runs a deployment, it
+will fetch the remote recipe and create a directory for it under `$ABRA_DIR`
+(typically `~/.abra`):
+
+```
+$ABRA_DIR/recipes/mygit_org_myorg_cool-recipe
+```