feat: add otel-demo tutorial

[suhyenim]

Proposed changes

This pull request introduces a tutorial on injecting chaos into the target application, otel-demo, using Litmus, and then collecting and observing the application's logs, metrics (including chaos metrics), and tracing through OpenTelemetry. The otel-demo consists of microservices written in various programming languages that communicate over gRPC and HTTP, along with a load generator that uses Locust to simulate user traffic. By following this tutorial, users will gain observability into both the chaos experiments and the target application. This tutorial aims to help users enhance their understanding of how chaos engineering can be integrated with observability practices to improve system resilience.

Tutorial Architecture

Tutorial Summary

1. Install litmus & Set up environments → Detail
2. Install target applications (otel-demo) → Detail
3. Install OpenTelemetry, Prometheus, Jaeger, Grafana → Detail
4. Set up probe & Perform chaos experiments
   • Experiment 1: pod-network-latency on cart service → Detail
     • This experiment is designed to fail.
   • Experiment 2: pod-delete on recommendation service → Detail
     • This experiment is designed to pass.
5. Observe chaos on Grafana
   • Experiment 1: pod-network-latency on cart service
     • Users can check cart service Spanmetrics Metrics.
       
     • Also, users can check the chaos experiment results.
       
   • Experiment 2: pod-delete on recommendation service
     • Users can check Error Rate in frontend service Spanmetrics.
       
     • Also, users can check the chaos experiment results.
       

Types of changes

What types of changes does your code introduce to Litmus? Put an x in the boxes that apply

• New feature (non-breaking change which adds functionality)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices applies)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the CONTRIBUTING doc
• I have signed the commit for DCO to be passed.
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added necessary documentation (if appropriate)

Dependency

This PR does not introduce any new dependencies.

Special notes for your reviewer:

[moggaa]

We have added more details to the PR description and included tutorial screenshots. Could you please review or check it?

[namkyu1999]

Run dorny/paths-filter@v3 pipeline failed because the paths-filter does not watch these changes paths. We can still review and merge this PR because this failure is not a fault.