All-numeric Kubernetes namespaces cannot be used with odo although they are valid for K8s

[rm3l]

/kind bug

What versions of software are you using?

Operating System:
Fedora 35

Output of odo version:
odo v2.5.0 (40f55eb)

How did you run odo exactly?

I tried to create and switch to a dedicated namespace named after an issue number, say 5646.
kubectl created the namespace without any issue, and I can easily use it.

However, running odo dev did not succeed, with the following validation errors:

[kind-local-k8s-cluster|5646] 
~/w/t/5620-devfile-with-container-component-command on  main [$?] via ☕ v17.0.2 on ☁️   
❯ odo dev     
  __
 /  \__     Developing using the my-component-with-command Devfile
 \__/  \    Namespace: 5646
 /  \__/    odo version: v2.5.0
 \__/

↪ Deploying to the cluster in developer mode
 ✗  Waiting for Kubernetes resources 
 ✗  Failed to create the component: component namespace "5646" is not valid, component namespace should conform the following requirements: 
- Contain at most 63 characters
- Contain only lowercase alphanumeric characters or ‘-’
- Start with an alphanumeric character
- End with an alphanumeric character
- Must not contain all numeric values

Expected behavior

It is clearly stated in the output that the namespace must not contain all numeric values, but I don't understand why we have such a requirement because the namespace name I tried to use is, I think, a valid RFC 1123 DNS name, as expected by Kubernetes.

Maybe there is a valid (but undocumented) reason for that limitation?

Any logs, error output, etc?

The validation error comes from a function located in the devfile/library library: https://github.com/devfile/library/blob/main/pkg/util/util.go#L1046

According to @feloy, the validation was introduced in #2699.
Also, we would need to beware of potential side effects, especially when handling YAML files.

As a side note, the odo dev command run above correctly quoted the namespace value in the .odo/env/env.yaml file after creating the file:

ComponentSettings:
  Name: my-component-with-command
  Project: "5646"
  AppName: app

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