Add User-Agent property to Serilog logging

[Copilot]

Overview

This PR enhances Serilog logging by including the User-Agent header from HTTP requests as a property in log events, improving traceability and diagnostics.

Changes

Updated HttpContextLogEventEnricher to extract the User-Agent header from incoming HTTP requests and add it as a property named "User-Agent" to all relevant Serilog log events.

Implementation Details

The implementation follows the existing pattern used for other HTTP context enrichment in the codebase:

• Checks if the User-Agent header exists in the HTTP request using httpContext.Request?.Headers?.TryGetValue()
• Only adds the property when the header is present (omitted when absent)
• Uses AddPropertyIfAbsent() to avoid conflicts if the property is already set
• Properly handles null checks with null-conditional operators

if (httpContext.Request?.Headers?.TryGetValue("User-Agent", out var userAgent) == true)
{
    logEvent.AddPropertyIfAbsent(propertyFactory.CreateProperty("User-Agent", userAgent.ToString()));
}

Benefits

• Improved diagnostics: Easier identification of request sources for troubleshooting
• Traffic analysis: Better visibility into client types and patterns
• Security auditing: Enhanced log information for security reviews
• Consistency: Logs now include standard HTTP metadata alongside existing properties like UserName

Testing

• ✅ Solution builds successfully with no errors or warnings
• ✅ Code formatting follows project standards defined in .editorconfig
• ✅ Implementation matches the pattern used in other services (e.g., TimeZoneService)

Fixes issue regarding User-Agent property in Serilog logging.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add "User-Agent" property to Serilog logging</issue_title>
<issue_description>Enhance Serilog logging by including a property named "User-Agent" that contains the User Agent string from the HTTP request, if available. This will improve traceability and diagnostics by identifying the source of requests.

Proposed Solution:

• Update the logging logic to extract the User Agent header from the HTTP request (if it exists).
• Add this value as a property named "User-Agent" in all relevant Serilog log events.

Benefits:

• Easier analysis of traffic patterns and troubleshooting.
• More informative logs for auditing and security review.

Acceptance Criteria:

• The "User-Agent" property is present in log entries when an HTTP request includes a User Agent header.
• If the header is absent, the property should be omitted or set to null/empty.
  </issue_description>

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

Fixes #33

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[Copilot]

Pull Request Overview

This PR enhances Serilog logging by adding User-Agent header information to log events for improved request traceability and diagnostics.

Key Changes

• Updated HttpContextLogEventEnricher to extract User-Agent headers from HTTP requests
• Added User-Agent as a log property when the header is present
• Implementation follows existing patterns in the codebase with proper null handling