Prepare for 1.5.60-beta1 release

[Aaronontheweb]

Summary

Prepare for 1.5.60-beta1 beta release to test the OpenTelemetry trace correlation feature merged after 1.5.59.

Changes

• Updated version to 1.5.60-beta1
• Added release notes for 1.5.60-beta1

Release Notes

Beta Release

This is a beta release for testing the OpenTelemetry trace correlation feature that was merged after 1.5.59.

New Features

• Add OpenTelemetry trace correlation support for LoggerFactoryLogger - enables proper trace correlation for logs emitted from actor code. Solves the problem that Activity.Current doesn't flow across actor mailbox boundaries because it uses AsyncLocal<T>. When using Akka.NET 1.5.59+, LogEvent.ActivityContext captures trace context at log creation time and flows it through to OpenTelemetry LogRecords via the new AkkaTraceContextProcessor. Register with options.AddAkkaTraceCorrelation() in your OpenTelemetry logging configuration.

Test plan

• Build script ran successfully
• Version updated to 1.5.60-beta1
• CI passes