Zap-Trace-Span is probably not used anymore

If I remember well the `Zap-Trace-Span` is something added when we tried tracing via logs.
Are we sure this is still usual? It is a requirement we expose via API and via Swagger, so it means documentation and generated code as a consequence.

@nathanielc were you involved?

Start by searching the API and Swagger definitions for `Zap-Trace-Span`, then check whether the requirement is still used by the tracing or logging paths. Done means confirming its status and, if obsolete, removing the API requirement together with the affected documentation and generated code.

Written by the indexing model from the issue text.