Allow fine-tuning of gRPC server underneath of GrpcContainer

[armiol]

This changeset is a port of #1454 to master.

Disclaimer

Also, this is just a first of such "porting" PRs. To keep things going, we are going to use the current state of core-java:master, rather than wait until the whole machinery (ProtoData et al) unwinds in its full blossom. Therefore, config, dependencies and stuff will NOT be updated in scope of "porting".

What's Changed

Prior to this changeset, there was no convenient way to set some "native" properties of the gRPC server, which is running underneath Spine's GrpcContainer.

In particular, it is often needed to set the maximum size for the inbound messages. And it was nearly not possible to achieve, other than using a test-only GrpcContainer.injectServer() method. There is also a number of other configuration endpoints provided by the gRPC's ServerBuilder, which could not be accessed.

In this PR, the gRPC's ServerBuilder API becomes exposed like this:

GrpcContainer.atPort(1654)
             // `server` is an instance of `io.grpc.ServerBuilder`.
             .withServer((server) -> server.maxInboundMessageSize(16_000_000))
             // ...
             .build();

So, rather than copying the ServerBuilder's API in GrpcContainer, the direct access to the builder is provided. That will allow to be always up-to-date with the configuration capabilities of the gRPC Server, rather than copying and chasing their API in the gRPC releases to come.

However, as of this PR, the GrpcContainer.Builder.withServer(...) method is marked as @Experimental. The reason is that the "native" ServerBuilder API allows to perform some destructive actions. Therefore, the decision to expose it as-is is not yet final.

[codecov]

Codecov Report

Merging #1510 (ec5c160) into master (936f719) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1510      +/-   ##
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+ Coverage     89.68%   89.70%   +0.01%     
- Complexity     4902     4904       +2     
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  Files           631      631              
  Lines         15305    15312       +7     
  Branches        883      884       +1     
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+ Hits          13726    13735       +9     
+ Misses         1273     1271       -2     
  Partials        306      306              

[alexander-yevsyukov]

LGTM, which one minor suggestion.

[alexander-yevsyukov]

Can we have .newBuilder() on the previous line, please?

Probably, we need to have a test fixture which would read something like CommandSerice.noOp() or CommandService.servingNoCommands().

[armiol]

I have refrained from creating a fully-fledged fixture set, as we only have such cases thrice in two different tests. But I have created a new Given... on this matter.