Validation doesn't allow stored impressions without bidders

[muuki88]

We faced an issue with stored impressions that are not configured, but requested and thus crash the entire auction.

prebid-server-java/src/main/java/org/prebid/server/validation/RequestValidator.java

Lines 995 to 1001 in ed1baac

	if (extPrebidBidder == null) {
	if (storedAuctionResponse != null) {
	return;
	} else {
	throw new ValidationException("request.imp[%d].ext.prebid.bidder must be defined", impIndex);
	}
	}

This validation doesn't allow us to create a stored impression that looks like this

{
  "id" : "123/content_1",
  "banner" : {
    "format" : [  ]
  },
  "ext" : {  }
}

instead we have to do something like this

{
  "id" : "123/content_1",
  "banner" : {
    "format" : [ ]
  },
  "ext" : {
    "h5": {} // this bidder does not exist, but tricks the validation
  }
}

Proposal

It would be great to disable certain validations. E.g.

validations:
  allow:
    - empty-stored-impressions

[bretg]

@muuki88 - maybe we can just drop the whole validation? No clear to me that a validation like this is real valuable because it's already in the DB and this error isn't that much more helpful than just noticing that there aren't any bidders in the auction.

[muuki88]

That would be even better IMHO. Because this escalates an error ( or purposely configured ad unit ) to the entire auction.

[bretg]

Care to submit a PR @muuki88 ?

[muuki88]

Deleting code? Always 😍😎

[bretg]

Would like to discuss with the committee whether we should continue to hard-fail on missing imp[%d].ext.prebid.bidder.

We already have the scenario where bidders get removed due to lack of Purpose 2 consent - it's possible to take the view that the request/storedrequest should be allowed to not contain bidders.