docs: publish v3.0 feature docs

docs/versioned_docs/version-v3.0.0/01-index.md

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+---
+title: "Arcus Observability"
+layout: default
+slug: /
+sidebar_label: Welcome
+---
+
+# Introduction
+
+Arcus Observability allows you to work easily with Azure Application Insights telemetry by making use of the common `ILogger` infrastructure to track dependencies, log custom metrics and log multi-dimensional telemetry data. The library supports multiple telemetry types like tracking dependencies, requests, events, metrics, while also be able to filter with Serilog filters and enrich with custom correlation.
+
+![Logger Arcus - Application Insights](/img/logger-arcus-appinsights.png)
+
+# Guidance
+
+- [Using Arcus & Serilog in ASP.NET Core](./02-Guidance/use-with-dotnet-and-aspnetcore.md)
+- [Using Arcus & Serilog in Azure Functions](./02-Guidance/use-with-dotnet-and-functions.md)
+
+# Installation
+
+The Arcus.Observability.Correlation package can be installed via NuGet:
+
+```shell
+PM > Install-Package Arcus.Observability.Serilog.Sinks.ApplicationInsights
+```
+
+For more granular packages we recommend reading [the documentation](./03-Features/sinks/azure-application-insights.md).
+
+# License
+This is licensed under The MIT License (MIT). Which means that you can use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the web application. But you always need to state that Codit is the original author of this web application.
+
+*[Full license here](https://github.com/arcus-azure/arcus.observability/blob/master/LICENSE)*

docs/versioned_docs/version-v3.0.0/02-Guidance/Service-to-service Correlation/index.md

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+---
+title: "Service-to-service correlation?"
+layout: default
+---
+
+# Service-to-service correlation
+The concept of service-to-service correlation is big and complex and spans multiple Arcus libraries. This user-guide will walk through all the available Arcus features that work together to facilitate service-to-service correlation in your application.
+
+## What is service-to-service correlation?
+Service-to-service correlation is a way to describe a relationship between different components where each 'component' represents a separate application. This could be, for example, an API call that results in an Azure Service Bus message that will be picked up by a message pump, or an Azure Function that calls an additional API after receiving a message from a queue.
+
+Anytime one application calls another, that's where service-to-service correlation comes in. This way of correlation makes sure that the relationship of a single (business) transaction doesn't stop at the borders of one application or component, but continues in the other application. The end result is a clear overview of all the components involved.
+
+![Arcus service-to-service application map](/media/service-to-service-correlation-application-map.png)
+
+When using Arcus for service-to-service correlation, you'll see the this relationship in Application Insights in the [end-to-end transaction view](https://docs.microsoft.com/en-us/azure/azure-monitor/app/transaction-diagnostics):
+
+![Arcus service-to-service correlation relationship](/media/service-to-service-correlation-relationship.png)
+
+## Why should I use service-to-service correlation?
+Adding service-to-service correlation to your application adds many advantages:
+* ✔ Quickly spot performance bottlenecks and failures
+* ✔ Clear overview of used (Azure) resources
+* ✔ Effective architectural decision-making on application flow
+
+## What Arcus components support service-to-service correlation?
+Currently, we support service-to-service correlation with several types of components:
+* [Arcus Web API](https://webapi.arcus-azure.net/features/correlation)
+* [Arcus Azure Service Bus message pump/router](https://messaging.arcus-azure.net/)
+* And [other built-in and custom dependencies](https://observability.arcus-azure.net/Features/writing-different-telemetry-types)
+
+We're working on adding Azure EventHubs message pump to the mix.
+
+> ⚠ Service-to-service correlation is only available for Azure Functions that run in-process. Out-of-process / isolated Azure Functions doesn't have (yet) the necessary built-in Arcus functionality to facilitate service-to-service correlation.
+
+> ⚠ Service-to-service correlation is currently only supported for projects that uses Application Insights as their Serilog logging system. If you want to use Arcus' service-to-service functionality outside Application Insights, [please let us know](https://github.com/arcus-azure/arcus.observability/issues/new/choose).
+
+## How do I add service-to-service correlation to my application components?
+Service-to-service correlation should be added on both the sending and receiving components of your project so the internal Arcus functionality can link the request/response correctly in Application Insights. The following user-guides will go over the sending and receiving side of Web API's and Azure Service Bus resources:
+
+* [Use service-to-service correlation in Web API solutions](use-service-to-service-correlation-in-web-api.md)
+* [Use service-to-service correlation in Service Bus solutions](use-service-to-service-correlation-in-service-bus.md)