Restrict critical parameters for PG tool (#2156)

[xiangyan99]

• Added parameter allowlist validation for the PostgreSQL server param set command to restrict modifications to safe, non-security-critical parameters only

• update

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Cherry pick 4b2ea77

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Pre-merge Checklist

• Required for All PRs
  • Read contribution guidelines
  • PR title clearly describes the change
  • Commit history is clean with descriptive messages (cleanup guide)
  • Added comprehensive tests for new/modified functionality
  • Created a changelog entry if the change falls among the following: new feature, bug fix, UI/UX update, breaking change, or updated dependencies. Follow the changelog entry guide
• For MCP tool changes:
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  • Updated servers/Azure.Mcp.Server/README.md and/or servers/Fabric.Mcp.Server/README.md documentation
  • Validate README.md changes running the script ./eng/scripts/Process-PackageReadMe.ps1. See Package README
  • For new or modified tool descriptions, ran ToolDescriptionEvaluator and obtained a score of 0.4 or more and a top 3 ranking for all related test prompts
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• Extra steps for Azure MCP Server tool changes:
  • Updated command list in servers/Azure.Mcp.Server/docs/azmcp-commands.md
  • Ran ./eng/scripts/Update-AzCommandsMetadata.ps1 to update tool metadata in azmcp-commands.md (required for CI)
  • Updated test prompts in servers/Azure.Mcp.Server/docs/e2eTestPrompts.md
  • 👉 For Community (non-Microsoft team member) PRs:
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    • Manual tests run: added comment /azp run mcp - pullrequest - live to run Live Test Pipeline

[Copilot]

Pull request overview

This PR hardens the Azure MCP PostgreSQL tool’s server param set command by preventing updates to security-sensitive PostgreSQL server parameters, reducing the risk of prompt-injection/agent misuse.

Changes:

• Added a ServerParameterValidator that blocks updates to a set of security-sensitive PostgreSQL parameters by throwing CommandValidationException (403).
• Wired the validator into ServerParamSetCommand.ExecuteAsync to enforce the restriction before calling the service layer.
• Updated/added unit tests covering blocked parameters and validator behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
tools/Azure.Mcp.Tools.Postgres/tests/Azure.Mcp.Tools.Postgres.UnitTests/Server/ServerParamSetCommandTests.cs	Updates existing tests and adds new coverage for blocked parameters and validator edge cases.
tools/Azure.Mcp.Tools.Postgres/src/Validation/ServerParameterValidator.cs	Introduces a security-sensitive parameter blocklist validator that throws structured validation exceptions.
tools/Azure.Mcp.Tools.Postgres/src/Commands/Server/ServerParamSetCommand.cs	Enforces parameter validation prior to executing the parameter update service call.
servers/Azure.Mcp.Server/changelog-entries/1774291948051.yaml	Adds a changelog entry describing the new parameter restriction behavior.