Option to do array merges on bcat and badv

[ollyburns]

The proposal is to extend the feature in issue 4111 to also allow bcat and badv to be merged. This would be set at account level.

The use case is when the publisher is already sending a list of block advertisers or categories and the host company wants to add to these lists using a stored request, server side.

Discussed in PMC 17th Dec 2025. There was agreement in principle.