feat: add APMBatch protobuf message

[kruskall]

Add a protobuf definition for APMBatch and generate models

[inge4pres]

I noticed we already have a "Batch" type defined here
https://github.com/elastic/apm-data/blame/f171078e95faa52f34fc6f91c07c54f3de2cd40c/model/modelpb/batch.go#L46

Is the generated code different with the proposed change?

[kruskall]

I noticed we already have a "Batch" type defined here
https://github.com/elastic/apm-data/blame/f171078e95faa52f34fc6f91c07c54f3de2cd40c/model/modelpb/batch.go#L46

Is the generated code different with the proposed change?

Yes. The modelpb.APMBatch in this PR is a protobuf message which can be marshaled/unmarshaled.

the modelpb.Batch type you linked is an alias for a slice of APMEvents and it's what is being passed down to the batch processors.

[inge4pres]

the modelpb.Batch type you linked is an alias for a slice of APMEvents and it's what is being passed down to the batch processors.

Thanks, I'll read further on your previous work to understand how we're going from one to another (the list of APMEvent to the Batch), because we don't want to have a breaking API change correct?