Add a config_file argument to the gateway launchfile to allow using an external config file.

[evTessellate]

…

Pull Request

Summary

Added an optional config_file argument to the ros2_mekdit_gateway to be able to set the gateway parameters from outside the ros2_mekdit_gateway. This feature is proposed for large projects where the gateway config lives in another bringup package and needs to be feed to the gateway.

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Issue

Link the related issue (required):
No issues, its new feature.

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Type

• Bug fix
• [X ] New feature or tests
• Breaking change
• Documentation only

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Testing

How was this tested / how should reviewers verify it?:

I launched the gateway with and without the new config_file orverride:

launch:
  - include:
      file: $(find-pkg-share ros2_medkit_gateway)/launch/gateway.launch.py

and

launch:
  - include:
      file: $(find-pkg-share ros2_medkit_gateway)/launch/gateway.launch.py
      arg:
        - name: config_file
          value: "$(find-pkg-share bringup_package)/config/medkit_config/gateway_params.yaml"    

In my gateway_params.yaml from my bringup_package, I enable the CORS parameters. So when I launched the gateway without the config file, the rosout log showed that CORS was disabled, and when I launched with the config_file, the log said CORS was enabled.

Also, I did all the test in https://github.com/selfpatch/ros2_medkit/blob/main/CONTRIBUTING.md with success.

Since no code had to be build, there wasn't that much build test to do.

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Checklist

• Breaking changes are clearly described (and announced in docs / changelog if needed)
• Tests were added or updated if needed
• Docs were updated if behavior or public API changed

[bburda]

Nice, backward-compatible addition - defaulting config_file to the packaged config keeps existing launches unchanged.

One thing before merge: docs. config_file is a new public launch argument and isn't documented - the README has a launch-args table for gateway_https.launch.py, and gateway.launch.py should get an equivalent entry. Please also call out the replace semantics there (see inline).

Out of scope, your call: gateway_https.launch.py uses the same parameters=[default_config, {...}] pattern and could take the same config_file arg for parity.

[bburda]

Worth documenting: when config_file is overridden the packaged gateway_params.yaml is no longer loaded at all - only the supplied file is. Any parameter absent from it falls back to the node's compiled-in declare_parameter defaults, not to the packaged YAML values. So the external file has to be a complete gateway config, not a fragment - a partial file would silently run with default discovery / auth / fault-manager / plugin settings.

gateway.launch.py doesn't have a launch-args table in the README yet (only gateway_https.launch.py does). Could you add one near the Configuration Examples section, e.g.:

### Launch Arguments (`gateway.launch.py`)

| Launch Argument       | Default                               | Description                                                                                                  |
| --------------------- | ------------------------------------- | ------------------------------------------------------------------------------------------------------------ |
| `config_file`         | packaged `config/gateway_params.yaml` | Path to the YAML parameter file. **Replaces** the packaged config entirely - must be a complete gateway config, not a fragment. |
| `server_host`         | `127.0.0.1`                           | Host to bind the REST server (`127.0.0.1` or `0.0.0.0`).                                                      |
| `server_port`         | `8080`                                | Port for the REST API.                                                                                       |
| `refresh_interval_ms` | `30000`                               | Safety-backstop refresh interval in ms (graph events drive the primary refresh).                             |

Use a config file from another package:

```bash
ros2 launch ros2_medkit_gateway gateway.launch.py \
  config_file:=$(ros2 pkg prefix my_bringup)/share/my_bringup/config/gateway_params.yaml
```

[bburda]

nit: typo overide -> override in the variable name.