Optional ad campaign id and ad attribution data

[kdzwinel]

Ad attribution data and ad campaign id are both required parameters while they don't seem to be required to provide meaningful feedback e.g.:

• ad click destination may not want to share any details with ad click source besides the fact that conversion happened,
• ad click destination origin might be enough for ad click source to identify a campaign.

In both cases 0 can be provided as the value of the unused parameter, but it would be more elegant to make those fields optional instead.

[annevk]

Wouldn't that give an additional bit? (Defaulting to 0 seems reasonable.)

[johnwilander]

With Anne's suggestion, this seems fine. We should make this change.