failure to parse quantities that are in nano units (e.g. nanocpus)

[philgebhardt]

Hello there. First of all, I must say thank you for creating this crate! This project provides useful operations around Kubernetes quantities and your work here is very-much appreciated.

I've found an issue in using it to parse quantities returned from metrics-server, which is reporting quantities in nanocpus. The error manifests as the following when I try to produce a ParsedQuantity from a Quantity.

ParsingFailed(Error(Error { input: "n", code: Tag }))

An example of what is produced by the metrics API:

PodMetrics {
    metadata: ObjectMeta {
        annotations: None,
        creation_timestamp: Some(
            Time(
                2024-07-29T21:58:30Z,
            ),
        ),
        deletion_grace_period_seconds: None,
        deletion_timestamp: None,
        finalizers: None,
        generate_name: None,
        generation: None,
        labels: Some(
            {
                "app": "test",
            },
        ),
        managed_fields: None,
        name: Some(
            "test",
        ),
        namespace: Some(
            "default",
        ),
        owner_references: None,
        resource_version: None,
        self_link: None,
        uid: None,
    },
    timestamp: "2024-07-29T21:58:22Z",
    window: "12.450808s",
    containers: [
        PodMetricsContainer {
            name: "test",
            usage: PodMetricsContainerUsage {
                cpu: Quantity(
                    "1836507n",
                ),
                memory: Quantity(
                    "8480Ki",
                ),
            },
        },
    ],
}