Merge branch 'afontaine/document-unleash-proxy' into 'master'

Document how to connect with Unleash Proxy

See merge request gitlab-org/gitlab!72321

doc/operations/feature_flags.md

@@ -403,6 +403,29 @@ else
 end
 ```
 
+### Unleash Proxy example
+
+As of [Unleash Proxy](https://docs.getunleash.io/sdks/unleash-proxy) version
+0.2, the proxy is compatible with feature flags. To run a Docker container to
+connect to your project's feature flags, run the following command:
+
+```shell
+docker run \
+  -e UNLEASH_PROXY_SECRET=<secret> \
+  -e UNLEASH_PROXY_URL=<project feature flags URL> \
+  -e UNLEASH_PROXY_INSTANCE_ID=<project feature flags instance ID> \
+  -e UNLEASH_PROXY_APP_NAME=<project environment> \
+  -e UNLEASH_PROXY_API_TOKEN=<token>
+```
+
+| Variable                    | Value                                                                                                                                |
+| --------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ |
+| `UNLEASH_PROXY_SECRET`      | Shared secret used to configure an [Unleash Proxy client](https://docs.getunleash.io/sdks/unleash-proxy#how-to-connect-to-the-proxy). |
+| `UNLEASH_PROXY_URL`         | Your project's API URL. For more details, read [Get access credentials](#get-access-credentials). |
+| `UNLEASH_PROXY_INSTANCE_ID` | Your project's Instance ID. For more details, read [Get access credentials](#get-access-credentials). |
+| `UNLEASH_PROXY_APP_NAME`    | The name of the environment the application runs in. For more details, read [Get access credentials](#get-access-credentials). |
+| `UNLEASH_PROXY_API_TOKEN`   | Required to start the Unleash Proxy, but not used to connect to GitLab. Can be set to any value. |
+
 ## Feature Flag Related Issues **(PREMIUM)**
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/36617) in GitLab 13.2.