OpenTelemetry OTLP log ingest

Accepts OTLP HTTP logs in JSON format.

Requests with Content-Type: application/x-protobuf are rejected with 415 Unsupported Media Type.

# OTEL Collector config:
exporters:
  otlp_http:
    endpoint: http://lynxdb:3100/api/v1/otlp
    encoding: json