Improve parameter option encoding/decoding

[liggitt]

Follow up from #21398

Parameter encoding/decoding follows an odd and asymmetric path today:

Encoding:

runtime.NewParameterCodec(...).EncodeParameters(runtime.Object, destination groupversion)
  -> queryparams.Convert(runtime.Object)
    uses json tag names as parameter names
    primitive values are added as query parameter string values
    struct values (currently only unversioned.Time) can convert themselves to a query parameter string value

Decoding:

runtime.NewParameterCodec(...).DecodeParameters(url.Values, source groupversion, destination object)
  -> conversion.convert(url.Values, versioned destination object)
    uses defined conversion functions between `*[]string` and field types to convert url query parameters to options structs

I'm not sure we want lots of arbitrary struct->queryparam serialization, but these paths should be more unified.

cc @smarterclayton

[techtonik]

Is there anything going on about this ticket?

[liggitt]

not currently, no

[techtonik]

@liggitt any ideas how to make parameters encoding/decoding symmetric?

[techtonik]

If I understand correctly. golang allow to annotate structures, and these annotations could be used for operations. What I don't like about the API is that it operates on parameters indirectly.

runtime.NewParameterCodec(...).DecodeParameters()

It would be more readable for me to see:

runtime.params = UpdateFromPOST()

or something like this.

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[liggitt]

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