Union cases based on values other than strings

[Happypig375]

I would like to model this:

[
{ "ID":"869E4854AB1A4251A370D482AE008089", "Name":"Item 1", "Type": 1 },
{ "ID":"83491C1E89334D2884E38021FA13A470", "Name":"Item 3", "Type": 1 },
{ "ID":"2E11A606C25D4FF99D08119B6B8E6576", "Name":"Item 8", "Type": 1 },
{ "ID":"EBEBBF9200844AD6B029EC4144174F47", "Name":"Item 12", "Type": 2, "Color": "Red", "Shape": "Circle" },
{ "ID":"647BC6470FD34666AF2DA020A5467B1A", "Name":"Item 2", "Type": 2, "Color": "Green", "Shape": "Rectangle" },
{ "ID":"211CC8D0F80D4EAE8766FF6178266AE9", "Name":"Item 6", "Type": 3, "Price": 150, "Unit": "USD" },
{ "ID":"FFB46CD3530F48A58B3C08DC319CE0D4", "Name":"Item 5", "Type": 3, "Price": 40, "Unit": "GBP" },
]

Basically, there are multiple fields that are included or excluded together depending on the type.
Modelling this with Skippable cannot guarantee that multiple fields must exist or not together,
while modelling this with Untagged throws an exception upon encountering common fields.
The best way to model this is with InternalTag ||| UnwrapRecordCases, but JsonPropertyName only supports strings, instead of bools, ints, floats, and nulls, or even via absence of the case name. I would like to see this supported.

[Happypig375]

I suppose an implementation would allow:

type [<JsonFSharpConverter(JsonUnionEncoding.InternalTag ||| JsonUnionEncoding.UnwrapRecordCases, unionTagName="Type")>] Item =
| [<JsonUnionTag 1>] T1 of {| ID:string; Name:string |}
| [<JsonUnionTag 2>] T2 of {| ID:string; Name:string; Color:string; Shape:string |}
| [<JsonUnionTag 3>] T3 of {| ID:string; Name:string; Price:float; Unit:string |}
| [<JsonUnionTag "abc">] T4 of {| ID:string |} // Same as [<JsonPropertyName "abc">] T4 of {| ID:string |}
| [<JsonUnionTag true>] T5 of {| ID:string |}
| [<JsonUnionTag null>] T6 of {| ID:string |}
| [<JsonUnionTag>] T7 of {| ID:string |} // Default case

[Happypig375]

Also, multiple tags should be allowed when deserializing, and the first attribute will be used when serializing.

[Tarmil]

This was added as JsonName in v1.0.