json: ser/de bytes as base64 strings not an array of bytes

[adriangb]

I believe this is how the proto <-> json spec defines that binary data should be handled: https://protobuf.dev/programming-guides/json/

I confirmed by exporting data from Python:

from opentelemetry.proto.collector.trace.v1.trace_service_pb2 import ExportTraceServiceRequest
from opentelemetry.proto.common.v1.common_pb2 import AnyValue, KeyValue
from opentelemetry.proto.resource.v1.resource_pb2 import Resource
from opentelemetry.proto.trace.v1.trace_pb2 import ResourceSpans
from google.protobuf.json_format import MessageToJson


export = ExportTraceServiceRequest(
    resource_spans=[
        ResourceSpans(
            resource=Resource(
                attributes=[
                    KeyValue(key="key", value=AnyValue(bytes_value=b"value"))
                ]
            )
        )
    ]
)

json = MessageToJson(export, use_integers_for_enums=True)

print(json)

with open("export.json", "w") as f:
    f.write(json)

{
  "resourceSpans": [
    {
      "resource": {
        "attributes": [
          {
            "key": "key",
            "value": {
              "bytesValue": "dmFsdWU="
            }
          }
        ]
      }
    }
  ]
}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.1%. Comparing base (5b86b7f) to head (8905a39).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2471   +/-   ##
=====================================
  Coverage   77.1%   77.1%           
=====================================
  Files        124     124           
  Lines      23021   23021           
=====================================
  Hits       17771   17771           
  Misses      5250    5250           

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[adriangb]

I'm not familiar with the codebase so I took a guess as to where to apply the fix. I tried to add an integration test but I could not get a failure case to fail a test so I'm not sure if that's even in the right place either. Some pointers would be appreciated.