Consider deprecating @ConfSerialisers?

[gepron1x]

This way to declare serialisers forces you to use singletones. Those ones are not the best practice in the object oriented programming.
Since there's already a better solution, using ConfigurationOptions, i suggest deprecating @ConfSerialisers annotation, or, at least, showing another way in documentation.

[A248]

I agree with deprecating @ConfSerialisers. Another limitation of this annotation is that it intends for value serializers to be confined to the specific config interface annotated. This behavior doesn't seem very useful; in almost all cases, the serializers should be registered globally instead.

Since we've received no other feedback on this issue, the annotation will be deprecated in 1.3.0. For 2.0 we'll simply remove the annotation entirely. If absolutely needed, we can re-add it, but I highly doubt such would happen.