Change secret extensions to emit secret without JSON wrapping

[SteveL-MSFT]

PR Summary

While working with AzCLI team to produce secret extension, it became obvious that the extension should just emit the secret as-is to STDOUT without being wrapped in JSON as it provides no value and just needs to be deserialized. In the future, if there are properties to the secret, we can add a schema and add to SecretMethod definition to have something like kind to indicate the type of output expected. However, with this change ALL secret extensions MUST emit just the secret as plaintext to STDOUT with trailing newline. Multiple lines to STDOUT is an error.

While fixing that, I also noticed that the $schema for some extensions was using the resource schema instead of the extension schema, so fixed those as well. Also reformatted the use statement to make it more readable.

Manually tested with prototype azcli extension manifest:

{
    "$schema": "https://aka.ms/dsc/schemas/v3/bundled/extension/manifest.json",
    "type": "Microsoft.Azure.CLI/KeyVault",
    "version": "1.0.0",
    "description": "Retrieve secrets from Azure KeyVault",
    "secret": {
        "executable": "az.cmd",
        "args": [
            "keyvault",
            "secret",
            "show",
            {
                "vaultArg": "--vault-name"
            },
            {
                "nameArg": "--name"
            },
            "--query",
            "value",
            "--output",
            "tsv"
        ]
    }
}

[Copilot]

Pull Request Overview

This PR changes secret extensions to emit secrets directly as plaintext to STDOUT instead of being wrapped in JSON format. This simplifies the secret handling workflow and eliminates unnecessary serialization/deserialization steps.

• Removes JSON wrapping from secret extension output, requiring all secret extensions to emit plaintext directly
• Fixes schema references in extension manifests to use the correct extension schema instead of resource schema
• Updates test secret extensions to output plaintext instead of JSON-wrapped objects

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
extensions/test/secret/testSecret2.dsc.extension.json	Updates schema reference and description to reflect extension usage
extensions/test/secret/testSecret.dsc.extension.json	Updates schema reference and description to reflect extension usage
extensions/test/secret/secret.ps1	Removes JSON wrapping and outputs secret directly
extensions/bicep/bicep.dsc.extension.json	Fixes schema reference to use extension manifest schema
dsc_lib/src/extensions/secret.rs	Removes SecretResult struct as JSON wrapping is no longer needed
dsc_lib/src/extensions/dscextension.rs	Updates secret handling to process plaintext output directly and reformats use statements