Configurable targeting prefix

[bretg]

We've gotten feedback that some publishers want a different set of ad targeting prefixes than hb_. One example is that they already have line items setup and want to move to a different set. Another example is a 'bake-off' where they want to run their original managed service and a new managed service side-by-side.

It's not currently possible in PBS to define alternate prefixes for targeting output without creating a server-side module.

Here's a proposed way to make this configurable:

1. allow the request to contain ext.prebid.targeting.prefix: "blah_"
2. support an account-level configuration for this instead of requiring stored requests to contain ext.prebid.targeting. Suggestion: auction.targeting.prefix

If both request.ext.prebid.targeting.prefix and auction.targeting.prefix config are present, prefer the request value.

If the value of the prefix is longer then settings.targeting.truncate-attr-chars, ignore it and add a warning to ext.warnings.

Yes, this feature could result in unusable targeting if the prefix is too long and settings.targeting.truncate-attr-chars is not raised from the default of 20. User beware.

[simas-b]

There is also a closely related enhancement regarding making it possible to opt out of targeting, wanted to mention it for the context: #2030

[bretg]

Discussed in committee, split these features into two issues.

[bretg]

Done in PBS-Java 2.5