Support for Avro Serialization

[juanpedromoreno]

This PR brings support for Avro serialization.

Therefore, from now on, you can choose for your service (at @rpc level) the type of serialization. Currently: Avro or Protobuf.

@free
    @service
    trait FreesRPCService {

      @rpc(Avro) def unary(a: A): FS[C]

      @rpc(Protobuf)
      @stream[ResponseStreaming.type]
      def serverStreaming(b: B): FS[Observable[C]]

      @rpc(Protobuf)
      @stream[RequestStreaming.type]
      def clientStreaming(oa: Observable[A]): FS[D]

      @rpc(Avro)
      @stream[BidirectionalStreaming.type]
      def biStreaming(oe: Observable[E]): FS[Observable[E]]
    }

We are relying on avro4s for the binary serialization/deserialization.

[codecov-io]

Codecov Report

Merging #78 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #78   +/-   ##
=======================================
  Coverage   88.52%   88.52%           
=======================================
  Files          12       12           
  Lines         122      122           
=======================================
  Hits          108      108           
  Misses         14       14

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[raulraja]

👏