Describe your environment

• opentelemetry-cpp v1.8.3
• OTLP gRPC
• No SSL
• No OTLP env vars, just default settings

Steps to reproduce
I'm facing an issue with SSL after upgrade from v1.8.2 to v1.8.3 with my gRPC telemetry.
The error is:

E0315 15:58:51.193959723  145649 ssl_transport_security.cc:1501] Handshake failed with fatal error SSL_ERROR_SSL: error:1408F10B:SSL routines:ssl3_get_record:wrong version number.

So debugging and comparing the behavior of both versions, I noticed that in v1.8.2 OtlpGrpcExporterOptions constructor is setting as default use_ssl_credentials: false but in the new v1.8.3 this default constructor is setting to use_ssl_credentials: true

This looks like a behaviour change introduced by this refactoring handling Boolean environment variables #1982

Digging into the code to look the initialization of use_ssl_credentials in the constructor:

This method GetOtlpDefaultIsSslEnable() to initialize use_ssl_credentials is based on GetOtlpDefaultTracesIsInsecure():

The issue is in the default return value of the following methods:

• GetOtlpDefaultTracesIsInsecure()
  

  opentelemetry-cpp/exporters/otlp/src/otlp_environment.cc

  Line 251 in 15ab9ed

  return false;

• GetOtlpDefaultMetricsIsInsecure()
  

  opentelemetry-cpp/exporters/otlp/src/otlp_environment.cc

  Line 295 in 15ab9ed

  return false;

• GetOtlpDefaultLogsIsInsecure()
  

  opentelemetry-cpp/exporters/otlp/src/otlp_environment.cc

  Line 312 in 15ab9ed

  return false;

All these methods are returning by default false if no env vars are defined.
So a false return means, IS NOT insecure, then IS secure 🤯

I don't know the gRPC transpost must be by default secure or insecure, but if the default is secure then this behaviour was enforced in this version.

According to the specification:
Insecure: Whether to enable client transport security for the exporter's gRPC connection. This option only applies to OTLP/gRPC when an endpoint is provided without the http or https scheme

So, if the gRPC endpoint scheme returns 'http' or 'https' as the following default, I think this value should overrided:

What is the expected behavior?
Upgrade from v1.8.2 to v1.8.3 without issues.

What is the actual behavior?
Upgrade to v1.8.3 wrongly assumes that gRPC connection are using SSL and fails because no certificates are defined.

Additional context
As workaround I need to set the env var OTEL_EXPORTER_OTLP_INSECURE=true in order to do not use SSL