Add WithDefaultPrintLevel option to configure default log level for Print methods

[Copilot]

Problem

When Echo framework uses its internal logging methods (such as for server startup messages), it calls the Print and Printf methods without specifying a log level. This results in logs showing ??? or - instead of a proper log level:

2024-11-24T18:36:10Z ??? ⇨ http server started on [::]:9151

This happens because the current implementation always uses zerolog.NoLevel with a hardcoded level string of "-" for these methods.

Solution

This PR adds a new configuration option WithDefaultPrintLevel(level log.Lvl) that allows users to configure a default log level for Echo's Print methods. When configured, these methods will use the specified level instead of showing ???.

Usage

e := echo.New()
e.Logger = lecho.New(
    os.Stdout,
    lecho.WithTimestamp(),
    lecho.WithDefaultPrintLevel(log.INFO), // Print methods will use INFO level
)

Result:

2024-11-24T18:36:10Z INF ⇨ http server started on [::]:9151

Implementation Details

• Added defaultPrintLevel *log.Lvl field to Options and Logger structs
• Created WithDefaultPrintLevel(level log.Lvl) setter function
• Added printEvent() helper method to determine the appropriate zerolog event
• Updated Print, Printf, and Printj methods to use the configurable level
• When WithDefaultPrintLevel is not specified, behavior remains exactly the same (backward compatible)

Testing

• All existing tests pass, ensuring 100% backward compatibility
• Added comprehensive tests covering the new functionality
• Added specific backward compatibility verification tests
• Manual testing confirms the feature works as expected

Documentation

Updated README.md with:

• New option listed in "Available Options" section
• Dedicated "Default Print Level Configuration" section with examples
• Before/after comparison showing the improvement

This change is completely backward compatible and provides a clean solution to the "???" log level issue reported in the original issue.

Fixes #33

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