Remove pinned TLS 1.2 security protocol to enable modern TLS negotiation

[Copilot]

Problem

The code was explicitly pinning the TLS protocol version to 1.2 using:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

This hardcoded setting in the GenerateSnippetsAsync method prevented the application from:

• Negotiating newer, more secure TLS versions like TLS 1.3
• Leveraging modern security improvements in the .NET runtime
• Following current security best practices for .NET applications

Solution

Removed the explicit TLS version pinning from ApiDoctor.Console/Program.cs (line 1957). The application now relies on .NET 8.0's secure default behavior.

Benefits

1. Enhanced Security: The application can now use TLS 1.3 when available, which provides better security and performance compared to TLS 1.2

2. System-Managed Security: .NET 8.0 defaults to SecurityProtocolType.SystemDefault, which allows the operating system to automatically select the most secure protocol available

3. Backward Compatible: TLS 1.2 remains supported for connections to legacy servers, ensuring no breaking changes to existing functionality

4. Future-Proof: The application will automatically benefit from future TLS protocol improvements without requiring code changes

Technical Details

In modern .NET (Core 2.1+ and .NET 5+), the default SecurityProtocol is SystemDefault, which:

• Delegates TLS version selection to the operating system
• Supports TLS 1.2, TLS 1.3, and future protocols
• Follows Microsoft's recommended security practices
• Provides the best balance of security and compatibility

Testing

• ✅ All 62 existing unit tests pass
• ✅ Build completes successfully with no new warnings or errors
• ✅ No functional changes to application behavior

Fixes #<issue_number>

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Remove pinned TLS1.2 version from ServicePointMgr</issue_title>
<issue_description>https://github.com/OneDrive/apidoctor/blob/master/ApiDoctor.Console/Program.cs#L1936

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;</issue_description>

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

Fixes #306

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