Update dfp.buildVideoUrl to accept adserver url

[matthewlane]

Updates pbjs.adServer.dfp.buildVideoUrl to accept a video adserver url (similar to deprecated pbjs.buildMasterVideoTagFromAdserverTag function) with a url parameter on the input object:

var videoUrl = pbjs.adServers.dfp.buildVideoUrl({
  adUnit: videoAdUnit,
  url: 'https://pubads.g.doubleclick.net/gampad/ads?iu=/19968336/prebid_video_adunit...'
});

Also updates the function to work without prebid cache enabled when the input contains an object of querystring parameters by appending description_url to the output url:

// with usePrebidCache configured to false
var videoUrl = pbjs.adServers.dfp.buildVideoUrl({
  adUnit: videoAdUnit,
  params: { iu: '/19968336/prebid_video_adunit' }
});

[dbemiller]

Looks sensible to me, barring one open question.

[dbemiller]

Is there any reason we aren't supporting this? It seems legitimate to parse the URL, overwrite any params, stringify the URL, and then return it.

[dbemiller]

Looks good overall... few recommendations. Mostly about docs.

[dbemiller]

very good idea. This makes the cache & no-cache workflows much more smooth... I'm a little embarrassed I never thought of it.

[dbemiller]

Looks like the JSDoc types need some updating for this. The DfpVideoOptions still says that params is required, and doesn't mention url at all.

[dbemiller]

Thanks to @rmloveland's documentation in src/prebid.js, you can call this an AdapterBidResponse now.

[dbemiller]

This description_url validation block is basically copy/paste between buildDfpVideoUrl and buildUrlFromAdserverUrlComponents... would be more maintainable in a helper method.

[dbemiller]

Looks good.

There's one more thing I should point out about the Types... but I don't think it should hold up the PR or anything. Almost all the programmers I've worked with in loosely-typed languages do the same thing you did.

If the DfpVideoParams has optional params and url properties, then that type implies that "both" or "neither" are also acceptable. But... what you really mean here is "must have one or the other, but not both."

In this case... it's probably better spec'd out as two types. One requires params, and the other requires url. The buildDfVideoUrl would accept either one (in JSDoc, {type1|type2}).

In any language, the golden standard for good types is "rejects all args which cause this function to error, and accept all args that allow this function to do its job."