Snapshot reference support

[linglingye001]

ref

[Copilot]

Pull request overview

This PR adds "Snapshot Reference" support to the Azure App Configuration Go provider. Snapshot references allow a key-value setting stored in App Configuration to point to a named snapshot — when loaded, the settings from that snapshot are merged into the configuration. The implementation refactors the existing snapshot loading into a shared helper function, adds content-type detection for snapshot references, and emits a tracing tag when they are used.

Changes:

• Extracts snapshot loading into a reusable loadSnapshotSettings function and adds snapshotSettingsLoader function type to support snapshot reference resolution with dependency injection.
• Adds detection of snapshotReferenceContentType in loadKeyValues, collects snapshot references, and resolves them via the new loadSettingsFromSnapshotRefs method.
• Adds UseSnapshotReference tracing option and SnapshotReferenceTag correlation context tag.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
azureappconfiguration/azureappconfiguration.go	Core implementation: detection of snapshot reference content type, loadSettingsFromSnapshotRefs, and parseSnapshotReference
azureappconfiguration/settings_client.go	Extracts snapshot loading into loadSnapshotSettings helper; adds snapshotSettingsLoader type
azureappconfiguration/internal/tracing/tracing.go	Adds SnapshotReferenceTag and UseSnapshotReference option to correlation context header
azureappconfiguration/constants.go	Adds snapshotReferenceContentType constant
azureappconfiguration/options.go	Minor whitespace fix
azureappconfiguration/snapshot_test.go	Adds unit tests for parseSnapshotReference and loadSettingsFromSnapshotRefs

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