[chore] Simplify the OTEL setup (#4110)

# Description

This simplifies our OTEL setup by:

* Getting rid of some deprecated things.
* Using `autoexport` and letting things get configured by the `OTEL_` environment variables.
* Removing all the unnecessary config options.

## Checklist

Please put an x inside each checkbox to indicate that you've read and followed it: `[ ]` -> `[x]`

If this is a documentation change, only the first checkbox must be filled (you can delete the others if you want).

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [ ] I/we have commented the added code, particularly in hard-to-understand areas.
- [x] I/we have made any necessary changes to documentation.
- [ ] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4110
Reviewed-by: tobi <kipvandenbos@noreply.codeberg.org>
Co-authored-by: Daenney <daenney@noreply.codeberg.org>
Co-committed-by: Daenney <daenney@noreply.codeberg.org>

1 files changed, 67 insertions, 0 deletions

diff --git a/vendor/go.opentelemetry.io/contrib/exporters/autoexport/registry.go b/vendor/go.opentelemetry.io/contrib/exporters/autoexport/registry.go
new file mode 100644
index 000000000..3d9abcafd
--- /dev/null
+++ b/vendor/go.opentelemetry.io/contrib/exporters/autoexport/registry.go
@@ -0,0 +1,67 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package autoexport // import "go.opentelemetry.io/contrib/exporters/autoexport"
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+)
+
+const otelExporterOTLPProtoEnvKey = "OTEL_EXPORTER_OTLP_PROTOCOL"
+
+// registry maintains a map of exporter names to exporter factories
+// func(context.Context) (T, error) that is safe for concurrent use by multiple
+// goroutines without additional locking or coordination.
+type registry[T any] struct {
+	mu    sync.Mutex
+	names map[string]func(context.Context) (T, error)
+}
+
+var (
+	// errUnknownExporterProducer is returned when an unknown exporter name is used in
+	// the OTEL_*_EXPORTER or OTEL_METRICS_PRODUCERS environment variables.
+	errUnknownExporterProducer = errors.New("unknown exporter or metrics producer")
+
+	// errInvalidOTLPProtocol is returned when an invalid protocol is used in
+	// the OTEL_EXPORTER_OTLP_PROTOCOL environment variable.
+	errInvalidOTLPProtocol = errors.New("invalid OTLP protocol - should be one of ['grpc', 'http/protobuf']")
+
+	// errDuplicateRegistration is returned when an duplicate registration is detected.
+	errDuplicateRegistration = errors.New("duplicate registration")
+)
+
+// load returns tries to find the exporter factory with the key and
+// then execute the factory, returning the created SpanExporter.
+// errUnknownExporterProducer is returned if the registration is missing and the error from
+// executing the factory if not nil.
+func (r *registry[T]) load(ctx context.Context, key string) (T, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	factory, ok := r.names[key]
+	if !ok {
+		var zero T
+		return zero, errUnknownExporterProducer
+	}
+	return factory(ctx)
+}
+
+// store sets the factory for a key if is not already in the registry. errDuplicateRegistration
+// is returned if the registry already contains key.
+func (r *registry[T]) store(key string, factory func(context.Context) (T, error)) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if _, ok := r.names[key]; ok {
+		return fmt.Errorf("%w: %q", errDuplicateRegistration, key)
+	}
+	r.names[key] = factory
+	return nil
+}
+
+func must(err error) {
+	if err != nil {
+		panic(err)
+	}
+}