Shared provider-passthrough route flow.
Passthrough routes keep the upstream provider API shape at the HTTP boundary while sharing common result dispatch and provider-error dispatch here.
Summary
Functions
@spec send_error( Plug.Conn.t(), term(), LLMProxy.HTTP.Routes.Passthrough.ErrorHandler.t() ) :: Plug.Conn.t()
@spec send_result( Plug.Conn.t(), LLMProxy.Providers.Result.t(), map(), String.t(), LLMProxy.HTTP.Routes.Passthrough.ResultHandler.t() ) :: Plug.Conn.t()