Langfuse OpenTelemetry example: env vars configuration issues with endpoint and auth header encoding

[dang-hai]

Issue Description

The environment variable configuration in langfuse/env.example doesn't work as documented. There are two main issues:

1. Endpoint URL format

The current env.example suggests using:

OTEL_EXPORTER_OTLP_ENDPOINT="https://us.cloud.langfuse.com/"

However, this didn't work for me. The endpoint needs to point directly to the traces API:

OTEL_EXPORTER_OTLP_TRACES_ENDPOINT="https://us.cloud.langfuse.com/v1/traces"

2. Authorization header encoding

The documentation is unclear about the required encoding format for the OTEL_EXPORTER_OTLP_HEADERS variable.

The auth token must be base64 encoded in the format: base64(public_key:secret_key)

Without proper base64 encoding, authentication always fails with an "invalid auth header" error.

The env.example should clarify this requirement or provide an example like:

# Encode your keys: echo -n "public_key:secret_key" | base64
OTEL_EXPORTER_OTLP_HEADERS="Authorization=Basic <base64_encoded_public_key:secret_key>"