Depends on D4089

Finally, using the add attachment reactor in the backup service.

• terminal 1

cd services
yarn run-blob-service-dev-mode

• terminal 2

cd services
yarn run-backup-service-dev-mode

• terminal 3

git clone https://github.com/karol-bisztyga/grpc-playground.git
cd grpc-playground
git checkout backup-async
./build.sh
./cmake/build/bin/client

• in terminal 3 create a new backup

n

• in terminal 3 create a new log

l

• in terminal 3, in order to append a new attachment holder to the backup, use the command b and for the log - k. After doing all this, check the target backup/log item in the database and see that the attachmentHolders filed is updated (for both items this field has the same name).