remove optional properties initializer

[xuzhg]

remove optional properties initializer.

[msftclas]

@xuzhg,
Thanks for your contribution as a Microsoft full-time employee or intern. You do not need to sign a CLA.
Thanks,
Microsoft Pull Request Bot

[PerthCharern]

What's the rationale behind these changes?

1. Why does type have to go on top?
2. Why are we removing the empty Servers, Tags, ExternalDocs?

[xuzhg]

1. It seems "type" is always existing in the schema. So, move it to top make the output document has better format.

2. Servers, Tags, ExternalDocs are optional properties.
   If we initialize them, the output document will have:

{
     "externaldocs": {},
     "tags": {}
}

this pr will avoid writing the empty optional object like this.

[PerthCharern]

For 1), I'm trying to make the properties written out in the same order as their appearance in the spec for clarity. Of course, this is not required, but it is useful for us as a sanity check to see whether all the properties have been taken care of in the WriteAsVX code. This should make maintaining that code easier in the future too. I also don't see the advantage of having "type" at the very top.

2. Makes sense.

---

In reply to: 344448632 [](ancestors = 344448632)

[xuzhg]

Ok for 1.

[xuzhg]

@PerthCharern So, I revert the "type" change.

[PerthCharern]