Initial QSfera import

Server/vendor/go.opentelemetry.io/otel/sdk/internal/x/README.md

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+# Experimental Features
+
+The SDK contains features that have not yet stabilized in the OpenTelemetry specification.
+These features are added to the OpenTelemetry Go SDK prior to stabilization in the specification so that users can start experimenting with them and provide feedback.
+
+These feature may change in backwards incompatible ways as feedback is applied.
+See the [Compatibility and Stability](#compatibility-and-stability) section for more information.
+
+## Features
+
+- [Resource](#resource)
+
+### Resource
+
+[OpenTelemetry resource semantic conventions] include many attribute definitions that are defined as experimental.
+To have experimental semantic conventions be added by [resource detectors] set the `OTEL_GO_X_RESOURCE` environment variable.
+The value set must be the case-insensitive string of `"true"` to enable the feature.
+All other values are ignored.
+
+<!-- TODO: document what attributes are added by which detector -->
+
+[OpenTelemetry resource semantic conventions]: https://opentelemetry.io/docs/specs/semconv/resource/
+[resource detectors]: https://pkg.go.dev/go.opentelemetry.io/otel/sdk/resource#Detector
+
+#### Examples
+
+Enable experimental resource semantic conventions.
+
+```console
+export OTEL_GO_X_RESOURCE=true
+```
+
+Disable experimental resource semantic conventions.
+
+```console
+unset OTEL_GO_X_RESOURCE
+```
+
+## Compatibility and Stability
+
+Experimental features do not fall within the scope of the OpenTelemetry Go versioning and stability [policy](../../../VERSIONING.md).
+These features may be removed or modified in successive version releases, including patch versions.
+
+When an experimental feature is promoted to a stable feature, a migration path will be included in the changelog entry of the release.
+There is no guarantee that any environment variable feature flags that enabled the experimental feature will be supported by the stable version.
+If they are supported, they may be accompanied with a deprecation notice stating a timeline for the removal of that support.

Server/vendor/go.opentelemetry.io/otel/sdk/internal/x/features.go

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+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Package x documents experimental features for [go.opentelemetry.io/otel/sdk].
+package x // import "go.opentelemetry.io/otel/sdk/internal/x"
+
+import "strings"
+
+// Resource is an experimental feature flag that defines if resource detectors
+// should be included experimental semantic conventions.
+//
+// To enable this feature set the OTEL_GO_X_RESOURCE environment variable
+// to the case-insensitive string value of "true" (i.e. "True" and "TRUE"
+// will also enable this).
+var Resource = newFeature(
+	[]string{"RESOURCE"},
+	func(v string) (string, bool) {
+		if strings.EqualFold(v, "true") {
+			return v, true
+		}
+		return "", false
+	},
+)
+
+// Observability is an experimental feature flag that determines if SDK
+// observability metrics are enabled.
+//
+// To enable this feature set the OTEL_GO_X_OBSERVABILITY environment variable
+// to the case-insensitive string value of "true" (i.e. "True" and "TRUE"
+// will also enable this).
+var Observability = newFeature(
+	[]string{"OBSERVABILITY", "SELF_OBSERVABILITY"},
+	func(v string) (string, bool) {
+		if strings.EqualFold(v, "true") {
+			return v, true
+		}
+		return "", false
+	},
+)
+
+// PerSeriesStartTimestamps is an experimental feature flag that determines if the SDK
+// uses the new Start Timestamps specification.
+//
+// To enable this feature set the OTEL_GO_X_PER_SERIES_START_TIMESTAMPS environment variable
+// to the case-insensitive string value of "true".
+var PerSeriesStartTimestamps = newFeature(
+	[]string{"PER_SERIES_START_TIMESTAMPS"},
+	func(v string) (bool, bool) {
+		if strings.EqualFold(v, "true") {
+			return true, true
+		}
+		return false, false
+	},
+)

Server/vendor/go.opentelemetry.io/otel/sdk/internal/x/x.go

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+// Code generated by gotmpl. DO NOT MODIFY.
+// source: internal/shared/x/x.go.tmpl
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Package x documents experimental features for [go.opentelemetry.io/otel/sdk].
+package x // import "go.opentelemetry.io/otel/sdk/internal/x"
+
+import (
+	"os"
+)
+
+// Feature is an experimental feature control flag. It provides a uniform way
+// to interact with these feature flags and parse their values.
+type Feature[T any] struct {
+	keys  []string
+	parse func(v string) (T, bool)
+}
+
+func newFeature[T any](suffix []string, parse func(string) (T, bool)) Feature[T] {
+	const envKeyRoot = "OTEL_GO_X_"
+	keys := make([]string, 0, len(suffix))
+	for _, s := range suffix {
+		keys = append(keys, envKeyRoot+s)
+	}
+	return Feature[T]{
+		keys:  keys,
+		parse: parse,
+	}
+}
+
+// Keys returns the environment variable keys that can be set to enable the
+// feature.
+func (f Feature[T]) Keys() []string { return f.keys }
+
+// Lookup returns the user configured value for the feature and true if the
+// user has enabled the feature. Otherwise, if the feature is not enabled, a
+// zero-value and false are returned.
+func (f Feature[T]) Lookup() (v T, ok bool) {
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/62effed618589a0bec416a87e559c0a9d96289bb/specification/configuration/sdk-environment-variables.md#parsing-empty-value
+	//
+	// > The SDK MUST interpret an empty value of an environment variable the
+	// > same way as when the variable is unset.
+	for _, key := range f.keys {
+		vRaw := os.Getenv(key)
+		if vRaw != "" {
+			return f.parse(vRaw)
+		}
+	}
+	return v, ok
+}
+
+// Enabled reports whether the feature is enabled.
+func (f Feature[T]) Enabled() bool {
+	_, ok := f.Lookup()
+	return ok
+}