[CON-3] Generic gRPC connector

[alexeyzimarev]

Send events to a gRPC endpoint.

Producing messages can be done using RPC calls or streaming. We'll start with RPC.

It needs a remote checkpoint store as well. The proto contract would need two service functions:

• Get the checkpoint
• Store the checkpoint

_CON-3

[canny[bot]]

This issue has been linked to a Canny post: Generic gRPC connector :tada: