Flexibility in X-Ray annotations regarding search

[BT-22]

Hello, the X-Ray collector supports index all attributes or index a list of attributes.
However, even if a list is used, still using SDK or CLI, one can send an annotation that is not on the list, which kind of defeating the purpose of the list in a way.

While that itself might be a separate issue, this question is more about the following:

When a trace has more than 50 annotations, only up to 50 are indexed and therefore searchable. Which 50? I'm not sure the answer / algorithm is in this repo...

Is it possible to allow some "plugin" code to work with the collector? So that one can enforce some own logic in reliably deciding in a trace which attributes are annotations? Or control the max number of annotations in a trace to be <= 50 (the index/search limit).

For example, maybe one wants to always have some 20 annotations in any trace, so one needs to detect and avoid some service sends another 31+ annotations to exceed the limit of 50.

Either way the goal is to make sure one doesn't end up with a trace with more annotations than X-Ray indexes - that would avoid the issue where search is made on an unindexed annotation by chance and finds nothing.