Lack of ConnectionString Support in HealthChecks.AzureApplicationInsights

[shayne-marriage-scp]

Issue: Lack of ConnectionString Support in HealthChecks.AzureApplicationInsights

Description

The HealthChecks.AzureApplicationInsights package currently supports only the InstrumentationKey for connecting to Azure Application Insights. However, Microsoft is deprecating the InstrumentationKey and recommends using the ConnectionString instead. Support for InstrumentationKey ends on March 31, 2025. To future-proof this package and ensure compatibility with Application Insights, it needs to add support for ConnectionString.

Expected Behavior

The package should allow users to specify a ConnectionString as an alternative to the InstrumentationKey for connecting to Azure Application Insights. InstrumentationKey property is marked Obsolete. This will align with Microsoft's guidance and deprecation plans /ApplicationInsights-dotnet/issues/2560.

Current Behavior

Currently, the package only accepts InstrumentationKey, which will soon become obsolete, potentially breaking integrations or requiring manual updates to align with Azure's requirements.

Suggested Solution

1. Add a ConnectionString parameter: Update the health check configuration to accept a ConnectionString for Azure Application Insights.
2. Deprecate the InstrumentationKey: Mark InstrumentationKey as deprecated, but keep it for backward compatibility until it’s removed entirely by Microsoft.
3. Documentation: Update the README and any other relevant documentation to reflect this change, providing usage examples with the ConnectionString.