[WIP] handle edge cases in the name query parameter

[Copilot]

• Analyze current codebase and understand the issue requirements
• Verify current code builds and tests pass
• Add comprehensive test cases for edge cases (whitespace, long names, control characters, special symbols)
• Update CreateGreeting function to handle input validation (trim, length limit, sanitization)
• Update HTTP handler to sanitize name parameter before logging
• Verify all tests pass and edge cases are handled correctly
• Test the running server to ensure proper behavior

Implemented comprehensive edge case handling for the name query parameter:

Input validation in CreateGreeting:

• Trims leading/trailing whitespace using strings.TrimSpace()
• Returns "Hello, Guest" if input is empty after trim
• Limits accepted name length to 100 characters (truncates longer names)
• Strips newline and control characters (ASCII 0-31, 127) and replaces with spaces

Logging safety in HTTP handler:

• Sanitizes name parameter before logging to prevent log injection
• Removes control characters that could break log formatting

Test coverage added:

• TestGreeting_WhitespaceOnly: handles spaces, tabs, newlines, mixed whitespace
• TestGreeting_LongName: truncates names longer than 100 characters
• TestGreeting_NewlineInjection: sanitizes control characters in names
• TestGreeting_SpecialSymbols: preserves valid special characters and Unicode
• TestGreeting_TrimWhitespace: properly trims various whitespace combinations

All existing tests continue to pass, ensuring backward compatibility.

Fixes #5.

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