Add upload-time support to links parsed from a JSON API

[zanieb]

Adds support for including the upload-time field from PyPI in the JSON output. This allows package managers to filter files by upload time.

For example:

❯ curl -s -H 'Accept: application/vnd.pypi.simple.v1+json' 'http://localhost:3141/root/pypi/+simple/black' | jq .files\[0]
{
  "filename": "black-18.3a0-py3-none-any.whl",
  "url": "http://localhost:3141/root/pypi/+f/718/3263650ba3071/black-18.3a0-py3-none-any.whl",
  "hashes": {
    "sha256": "7183263650ba3071034e90b40a1ea74abccbd32cf525cef6d7914479dbe7f2fb"
  },
  "requires-python": ">=3.6",
  "upload-time": "2018-03-14T21:30:34.781336Z"
}

I'd appreciate some guidance on where to add test coverage.

[fschulze]

I would advice you to wait with this feature. I'm doing a complete refactor of the storage backend which will make this much easier. Currently it is very hard to get right with backward compatibility, replication and what have you.

[fschulze]

Please keep this open though, it is a good use case to test my refactoring.

[zanieb]

No problem thanks for giving it a look.

I needed this personally, otherwise my package manager tests skip all of the wheels :) but I can just install from my fork for now.

Let me know if you need anything.