Merge pull request #515 from holochain/hotfix-unstable-countersigning…

…-in-hdk

hotfix: mention unstable-countersigning flag for hdk in 0.4 upgrade guide

src/pages/resources/upgrade/upgrade-holochain-0.4.md

@@ -146,7 +146,7 @@ The biggest change for 0.4 is that some features are marked `unstable` and aren'
 **If your DNA needs to call a host function that depends on an unstable feature**, you'll need to do two things:
 
 1. [Build a custom Holochain binary](https://github.com/holochain/holonix?tab=readme-ov-file#customized-holochain-build) with both the specific feature you need (see the list above) and `unstable-functions` enabled.
-2. Enable the `unstable-functions` flag for the `hdi` and `hdk` dependencies in your zomes' `Cargo.toml` files:
+2. Enable the `unstable-functions` flag for the `hdi` and `hdk` dependencies in your zomes' `Cargo.toml` files, and enable the `unstable-countersigning` flag for the `hdk` dependency if you need it:
 
     ```diff:toml
      [dependencies]
@@ -157,7 +157,7 @@ The biggest change for 0.4 is that some features are marked `unstable` and aren'
     ```diff:toml
      [dependencies]
     -hdk = { workspace = true }
-    +hdk = { workspace = true, features = ["unstable-functions"] }
+    +hdk = { workspace = true, features = ["unstable-functions", "unstable-countersigning"] }
     ```
 
 Note that you'll need to make sure your users are running your custom conductor binary. If you compile your zomes without `unstable-functions` enabled for `hdi` or `hdk`, users with the flag enabled in Holochain will still be able to use your hApp, but if you compile your zomes _with_ `unstable-functions`, users with the flag(s) disabled won't be able to use your hApp.