C++ Logger API does not compliant with the OTel Logs Data Model

[yijiem]

In the OTel Logs Data Model, it is specified that the Body field must support any type to preserve the semantics of structured logs emitted by the application: https://opentelemetry.io/docs/specs/otel/logs/data-model/#field-body. This is specifically useful for the application which logs a JSON-structured data i.e. map<string, any> as the Body. But the OTel C++ Logger API does not support such a case, it supports string_view or AttributeValue type in the Body (code) but neither of those can preserve the semantics of structured data.

Ideally, if the Logger API preserves the semantics of structured data, the structure should be preserved across the stack (e.g. from application to OTel collector via OTLP and eventually the structured data gets exported to the backend log store).

Seems like there is also an Event API for logging structured data. But it is still a WIP and is a specialized Log API and would have the same issue in opentelemetry-cpp since the current API does not support structured data.