Bucket-only artifacts

Hello.

I am configuring an artifact repository following the documentation [here](https://argoproj.github.io/argo-workflows/artifact-repository-ref/) as follows:
```
apiVersion: v1
kind: ConfigMap
metadata:
  annotations:
    workflows.argoproj.io/default-artifact-repository: default-artifact-repository
  name: argo-workflows-artifacts-repository
data:
  default-artifact-repository: |
    s3:
      bucket: default
keyFormat: common/{{ workflow.name }}
      endpoint: argo-workflows-artifacts.infra.svc.cluster.local:9000
insecure: true
      accessKeySecret:
        key: accesskey
        name: argo-workflows-artifacts
secretKeySecret:
        key: secretkey
        name: argo-workflows-artifacts
```

Whenever I overwrite the key `bucket` as described [here](https://argoproj.github.io/argo-workflows/key-only-artifacts/), the artifacts are still uploaded in bucket `default`.

```
apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
name: hello-world
spec:
artifactRepositoryRef:
configMap: argo-workflows-artifacts-repository
entrypoint: main
templates:
- name: main
container:
image: docker/whalesay:latest
command: [sh, -c]
args: ["cowsay hello world | tee /tmp/hello_world.txt"]
volumeMounts:
- name: tmp
mountPath: /tmp
volumes:
- name: tmp
emptyDir: {}
outputs:
artifacts:
- name: hello_world
path: /tmp/hello_world.txt
s3:
bucket: dev
```

I order to further debug it, I removed the key `s3.bucket` from my configMap and set it through the WorkFlowTemplate exclusively. This, however, return me the following error:

```
Error (exit code 1): failed to put file: Bucket name cannot be empty
```

How can I configure the bucket per WorkFlow or WorkFlowTemplate?

Start with the artifactRepositoryRef and the S3 bucket settings shown in the issue, then compare the linked artifact repository and key-only artifact documentation. Reproduce both ConfigMap and WorkflowTemplate configurations and trace how bucket values are selected; done means a per-Workflow or WorkflowTemplate bucket overrides the default, or the documentation clearly states the limitation.

Written by the indexing model from the issue text.