Azure App Configuration component does not expose contentType in configuration metadata #4308

Describe the feature

Expose the contentType field from Azure App Configuration in the returned configuration.Item.Metadata.

Azure App Configuration defines contentType as an attribute that describes how a configuration value should be interpreted (for example, application/json). Currently, although all fields are retrieved from Azure, the contentType field is not included in the metadata returned by the Dapr component.

According to the Azure App Configuration documentation:
https://learn.microsoft.com/en-us/azure/azure-app-configuration/concept-key-value#use-content-type

the contentType field is used to describe the type of the stored value and can be used by applications to correctly interpret configuration data.

Exposing contentType would allow applications to:

• distinguish between different value types (e.g., plain string vs JSON)
• apply appropriate parsing or handling logic based on the content type
• improve interoperability with Azure App Configuration, especially for .NET applications and scenarios relying on structured configuration values

This change would be backward-compatible and additive, as it only enriches the metadata without altering existing behavior.

As an initial step, it may be reasonable to always include contentType when present (similar to how label is currently handled).

Release Note

RELEASE NOTE: ADD Azure App Configuration component exposes contentType in configuration metadata