Pipeline API - how can I use plugins?

Hi,

In our company use case - we have > 50 repositories that need to share the same pipeline configuration. We don't want to replicate the `pipeline.yml` file on all repositories, but rather control the pipeline via API.

It seems like the API does not have the same features as the `pipeline.yml`.
For staters: I can't use plugins.

I tries to use the pipeline `PATCH` API to add a step like this:
```json
{
"steps": [
{
"label": "bazel-build",
"type": "script",
"plugins": [
{
"docker#v3.5.0": {
"image": "l.gcr.io/google/bazel:2.0.0",
"command": ["bazel", "build", "//..." ]
}
}
]
}
]
}
```
I got `200 OK` result but calling `GET` on the same pipeline showed that it ignored the `plugins` property.