Drop the User EID object if the all the ID values are empty

[Pubmatic-Supriya-Patil]

Prebid Server has validation on the user EIDS object where User.Id is a required field. There can be situations where the publisher has set a macro in the GAM tag for the User.Id field. For some requests, it's possible that this macro value is missing. Instead of returning a bad request, we can add a check to remove the Id field if it is not present.
Example
Valid EID:[{"source":"uidapi.com","uids":[{"id":"AgAACYa0cG2jcVcM42xG"}]}]
Invalid EID: [{"source":"uidapi.com","uids":[{"id":""}]}]
So with this, problem is like if we have mix of valid and invalid id's for same source then its returning invalid request.
Example: [{"source":"uidapi.com","uids":[{"id":""}, {"id":"AgAACYa0cG2jcVcM42xG"}]}, {"source":"liveramp.com","uids":[{"id":"AgAACYa0cG2jcVcM42xG"}]}, {"source":"yahoo.com","uids":[{"id":""},{"id":""}]}]

Here expectation is like valid id's should get considerd and invalid Id's can be dropped.

Example: [{"source":"uidapi.com","uids":[{"id":""}, {"id":"AgAACYa0cG2jcVcM42xG"}]}, {"source":"liveramp.com","uids":[{"id":"AgAACYa0cG2jcVcM42xG"}]}, {"source":"yahoo.com","uids":[{"id":""},{"id":""}]}]

After adding new logic to drop invalid ID's it should return valid ID's only like below

[{"source":"uidapi.com","uids":[{"id":"AgAACYa0cG2jcVcM42xG"}]}{"source":"liveramp.com","uids":[{"id":"AgAACYa0cG2jcVcM42xG"}]}]

If No valid id present then drop complete EIDS object
Example: [{"source":"uidapi.com","uids":[{"id":""}]}]

[bretg]

Discussed in committee. This sounds fine except that we'd also like warnings to be emitted when in debug mode:

• "removed EID uidapi.com due to empty ID"
• "removed empty EID array"

Received a clarification question:

do we need to add warning for each remove EID if eventually we remove the whole EIDs array?

I would say 'yes', there could be a series of warnings:

• "removed EID X due to empty ID"
• "removed EID Y due to empty ID"
• "removed EID Z due to empty ID"
• "removed empty EID array"

[Pubmatic-Supriya-Patil]

PR: #3891

[bretg]

Done with PBS-Java 3.13