The communication between the ShardRequestManager and the RsmClient
used to be direct. In this PR this changes into a future-based
communication type. The RsmClient stores state about the currently
processed future (either read or write request) and exposes blocking
and non-blocking functionality to obtain the filled future. The
ShardRequestManager -for now- will send of the set of requests present
in the ExecutionState and block on each of them until the requests are
completed or the set of paginated responses(caused by, for example the
batch-limit in ScanAll) are ready for the next round.
Create shard-side handlers for basic messages
Implement the handlers for CreateVertices, CreateEdges and ScanAll. Use
or modify the defined messages to interact with individual Shards and
test their behavior. Shard is currently being owned by ShardRsm
instances. The two top level dispatching functions Read() and Apply()
are responsible for read- and write operations respectively. Currently
there are a handful of messages that are defined but not utilized, these
will be used in the near future, as well as a couple of handler
functions with empty implementations.
