docs: Add guide to showcase handling outputs

Add a guide which highlights how to handle action's outputs by writing
them to the client filesystem and using CUE's integrations to marshal
them as JSON.

Signed-off-by: Marcos Lilljedahl <marcosnils@gmail.com>

docs/guides/1227-contributing.md

@@ -1,6 +1,6 @@
 ---
 slug: /1227/contributing
-displayed_sidebar: europa
+displayed_sidebar: 0.2
 ---
 
 # Contributing to Dagger

docs/guides/1228-handling-outputs.md

@@ -0,0 +1,28 @@
+---
+slug: /1226/handling-outputs
+displayed_sidebar: 0.2
+---
+
+# Handling action outputs
+
+It's most likely that upon executing a Dagger action, you'll find in the situation of having to parse some outputs. In Dagger 0.1 (pre-Europa), inputs and outputs had to be specifically defined; starting Dagger 0.2 (Europa) we introduced a brand new API which removed this capability temporarily until we come up with the [right UX](https://github.com/dagger/dagger/issues/1351) to bring this back. Until the API is ready, you can follow this guide which shows different **temporary** alternatives of parsing dagger outputs.
+
+## Writing outputs to the filesystem
+
+As showcased in the [interacting with the client](/1203/client) docs, Dagger already has the ability to write into the client filesystem through the `client` API. Using this capability we can then output any value into our local filesystem for further automation.
+
+Here's a simple example of a plain text output:
+
+```cue file=../tests/core-concepts/client/plans/output_simple.cue.fragment
+```
+
+After performing `dagger do test`, a new file named `output.txt` will be present in the current working directory with the output of the `bash.#Run` action.
+
+## Marshalling multiple outputs
+
+The above example works well for simple outputs, but most of the time some actions like [Netlify's](https://github.com/dagger/dagger/blob/main/pkg/universe.dagger.io/netlify/netlify.cue) can output mutiple values. In this case, Netlify's action is returning the deployment `url`, `deployUrl` and `logsUrl`. On this case, we can leverage on CUE's [default integrations](https://cuelang.org/docs/integrations/) and marshal all the values into a single `json` or `yaml` file.
+
+Here's an example on how to marshal multiple output values:
+
+```cue file=../tests/core-concepts/client/plans/output_marshal.cue.fragment
+```