feat(api): implement client-streaming during attestation push

[migmartri]

Currently, when we perform attestation push, we upload the whole recorded attestation, which can cause hit the max payload limit of 10MB

One way to not to run into this issue would be to implement client-streaming instead of unary.

https://grpc.io/docs/what-is-grpc/core-concepts/#client-streaming-rpc

[migmartri]

cc/ @jiparis @javirln

What do you think about this solution? I believe that this + #2126 would do the trick for scalability for now

[javirln]

Indeed, we can definitely switch to streaming on att push. We would just to double-check it's not use anywhere else so there is only one entrypoint for the streaming method.

[jiparis]

What about increasing the max payload size? why is not that a solution? In the near future we might want to support HTTP uploads using multipart.

[migmartri]

What about increasing the max payload size? why is not that a solution? In the near future we might want to support HTTP uploads using multipart.

max payload size is a ingress specific configuration, today we offer annotations for nginx only, so it's possible that our users on-prem will run into this issue if they try envoy or other ingress.

My reason to implement streaming is because is native, simple to implement and we'll reduce the pressure in the server during att push, which is an important step.

[migmartri]

@Piskoo feel free to take a look at it if you feel adventurous and or want to learn :)

One thing for sure though is that we should probably implement this method as another entry in the service, so we can keep the old Store method for older clients and just add a new one that supports streaming for the new clients.