Supporting non URL-encoded OTEL_EXPORTER_OTLP_HEADERS

[xrmx]

Is your feature request related to a problem?

As you can see from this table all language SDKs but python support non URL-encoded OTLP headers. Python SDK is respecting the spec but given that all other language SDKs prefer non url-encoded headers Python is an exception. That is a problem if you need to provide language agnostic instructions or documentation.

Describe the solution you'd like

Add support for non url-encoded OTLP headers env vars.

Describe alternatives you've considered

Rewrite headers in downstream distro code 😨

Additional Context

Discussed at 2024-08-01 SIG in favour on adding support for non-urlencoded headers in addition of the actual behaviour.

Would you like to implement a fix?

Yes