New Observability topic

[samsp-msft]

Summary

New document to provide an overview of Observability options and how to use Otel with .NET.

Shows metrics with prometheus & graphana and tracing with Jaeger.
Shows logs, metrics & tracing with app-insights

Fixes #Issue_Number (if available)

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Internal previews

📄 File	🔗 Preview link
docs/core/diagnostics/observability-with-otel.md	docs/core/diagnostics/observability-with-otel

[samsp-msft]

@bradygaster - I'd like your take on how deep we should go here
@mattmccleary - is there more info we should add here on OTel - I want to strike a balance of enough info here without having to update monthly based on new updates in OTel
@poppastring - I started adding dotnet-monitor, but as its not currently optimized for 24x7 egress, I don't know whether to include it or not.

[mattmccleary]

CC: @rajkumar-rangaraj @TimothyMothra @vishweshbankwar

[gewarren]

I made a bunch of suggestions to consider.

[gewarren]

I made a bunch of suggestions to consider.

[noahfalk]

Nice overview 👍

[samsp-msft]

@gewarren - I have a couple of benign warnings from the learn build service - I think they are what is blocking this.

• Line 118, Column 1: [Warning] Unrecognized language value '.csproj' in code snippet 'Snippet_References' in file 'snippets/OTel-Prometheus-grafana-Jaeger/csharp/OTel-Prometheus-Grafana-Jaeger.csproj'. Your code snippet might not render correctly. If this is the case, you can request a new value or use range instead.
• Line 388, Column 1: [Warning] Unrecognized language value '.csproj' in code snippet 'Snippet_AZMReferences' in file 'snippets/OTel-Prometheus-grafana-Jaeger/csharp/OTel-Prometheus-Grafana-Jaeger.csproj'. Your code snippet might not render correctly. If this is the case, you can request a new value or use range instead.
• Line 285, Column 232: [Suggestion] Link 'http://localhost:3000' points to a page that doesn't exist. Check the path or URL and update the link.
• Line 352, Column 49: [Suggestion] Link 'http://localhost:16686/' points to a page that doesn't exist. Check the path or URL and update the link.

The csproj work fine in the output, and the links are to services that are created by following the directions in the topic.

[meganbradley]

@gewarren @samsp-msft Is there an exception process for merging with warnings in the dotnet repo? It seems the blocker is a custom check for this repo - ordinarily PRs with warnings can be merged by someone with perms.

[gewarren]

@gewarren @samsp-msft Is there an exception process for merging with warnings in the dotnet repo? It seems the blocker is a custom check for this repo - ordinarily PRs with warnings can be merged by someone with perms.

@meganbradley Yes, I can remove that check from branch protection rules and merge this PR, but I don't want to have this warning in the repo because it will show up in other PRs too.