Support for Unknown status condition in Custom Resources

[EronWright]

What would you like to be added:
Improve support for producing a gauge for the status conditions of a custom resource, when the condition status is Unknown. Today, the data point cannot be produced due to a parse error:

[status,conditions]: [1]: [status]: strconv.ParseFloat: parsing \"Unknown\": invalid syntax

The gauge definition is:

    - name: "foo_status"
      help: "status condition "
      each:
        type: Gauge
        gauge:
          path: [status, conditions]
          labelsFromPath:
            type: ["type"]
          valueFrom: ["status"]

Why is this needed:
This is needed to round out the support for status conditions. Unknown is a legit status value and should be supported.

Describe the solution you'd like
it isn't totally clear what the gauge value should be. Here's a couple of options:

1. Don't report an error message and skip reporting the data point. This means that Unknown would translate into the absence of a data point.
2. Consider adding a valueMap structure to map the status values to a numerical value, e.g.

    - name: "foo_status"
      help: "status condition "
      each:
        type: Gauge
        gauge:
          path: [status, conditions]
          labelsFromPath:
            type: ["type"]
          valueFrom: ["status"]
          valueMap:
            - {from: "Unknown", to: 0}
            - {from: "True", to: 1}
            - {from: "False", to: 0}

[CatherineF-dev]

A related issue #1978, so that you can use cel to extract what you want.

[dgrisonnet]

/triage accepted
/assign @CatherineF-dev

[robbie-demuth]

I just ran into this issue and was able to workaround it by using a StateSet

- name: status_condition
  each:
    type: StateSet
    stateSet:
      path: [status, conditions]
      labelName: status
      valueFrom: [status]
      list: [True, False, Unknown]
      labelsFromPath:
        type: [type]

[defenestration]

I just ran into this issue and was able to workaround it by using a StateSet

- name: status_condition
  each:
    type: StateSet
    stateSet:
      path: [status, conditions]
      labelName: status
      valueFrom: [status]
      list: [True, False, Unknown]
      labelsFromPath:
        type: [type]

I feel like this suggestion should go into the docs here. Currently suggests using a Gauge for the status.conditions but this doesn't capture the 'unknown' status as suggested.