[EXPORTER] Boolean environment variables not parsed per the spec

[marcalff]

Per the spec:

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/sdk-environment-variables.md

boolean environment variables should accept "true" or "false", with case insensitive comparison.

Other values should cause a warnings.

Per the code:

inline bool GetOtlpDefaultIsSslEnable()
{
  constexpr char kOtlpTracesIsSslEnableEnv[] = "OTEL_EXPORTER_OTLP_TRACES_SSL_ENABLE";
  constexpr char kOtlpIsSslEnableEnv[]       = "OTEL_EXPORTER_OTLP_SSL_ENABLE";

  auto ssl_enable = opentelemetry::sdk::common::GetEnvironmentVariable(kOtlpTracesIsSslEnableEnv);
  if (ssl_enable.empty())
  {
    ssl_enable = opentelemetry::sdk::common::GetEnvironmentVariable(kOtlpIsSslEnableEnv);
  }
  if (ssl_enable == "True" || ssl_enable == "TRUE" || ssl_enable == "true" || ssl_enable == "1")
  {
    return true;
  }
  return false;
}

Issues:

• the string comparison is not case insensitive, for example TrUe should be true
• no warning is raised

Beside, this code has been copied and pasted all other the place, some cleanup is needed.

[github-actions]

This issue was marked as stale due to lack of activity.