[Mgmt Generator] Preserve specific extension scope information

[Copilot]

Description

Extension resources with specific parent scopes (e.g., Extension.ExternalResource<>) were being flattened to generic "Extension" scope, losing the specific parent resource type. This breaks C# path handling which interprets "Extension" as a generic scope parameter (/{scope}/providers/...).

Changes

Schema Extension

• Added optional specificExtensionScope field to ResourceMetadata in both TypeScript and C# schemas
• Captures extension type when scope is:
  • String literal: "Scope" or "ExternalResource"
  • ResolvedResource: parent resource type (e.g., "Microsoft.Compute/virtualMachines")

Emitter Updates

• Modified convertScopeToResourceScope() to return both ResourceScope enum and specificExtensionScope
• Updated convertResolvedResourceToMetadata() to populate new field from scope information

Testing

• Added test case validating specific extension scope preservation
• All existing tests pass (30 TypeScript, 91 C#)

Example

For a VM extension scoped to a VirtualMachine resource:

// Before: Lost specific parent information
{ resourceScope: "Extension" }

// After: Preserves parent resource type
{ 
  resourceScope: "Extension",
  specificExtensionScope: "Microsoft.Compute/virtualMachines"
}

The field is optional and backward compatible. C# generator can leverage this in future enhancements to correctly handle specific extension scenarios.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>[Azure Mgmt Generator] Support "specific extension"</issue_title>
<issue_description>Now our generator just make resources with "specific extension" as "Extension". This information is not enough.
For instance, for a resource like this:

alias VM = Extension.ExternalResource<>;

resolveArmResources returns a ResolvedResource with a specific "external resource" as its scope, but we did not handle it now, therefore it will have a scope of "Extension".
This could also happen when the resource is written by using a complicated "legacy operation".

This causes an issue in the C# part because C# part actually understands the "Extension" as scope as a resource path like those with scope parameters: /{scope}/providers/...

Therefore we need to refine both parts to make things correct.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Azure Mgmt Generator] Support "specific extension" #54706

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