♻️ [Refactor]: logger/middleware to Eliminate Code Duplication

[sixcolors]

Feature Description

Refactor the logger middleware in Fiber to adher to the "Don't Repeat Yourself" (DRY) principle. During recent discussions #2561, it was identified that the current implementation involves duplicated code for custom and default logger functions.

Additional Context (optional)

Code Refactoring: The primary focus is to eliminate code duplication by consolidating the common logic shared between custom and default logger functions. This not only improves code maintainability but also ensures consistent behavior across different configurations.

Code Snippet (optional)

// Default output when no custom Format or io.Writer is given
		if cfg.Format == ConfigDefault.Format {
			// Format error if exist
			formatErr := ""
			if cfg.enableColors {
				if chainErr != nil {
					formatErr = colors.Red + " | " + chainErr.Error() + colors.Reset
				}
				_, _ = buf.WriteString( //nolint:errcheck // This will never fail
					fmt.Sprintf("%s |%s %3d %s| %7v | %15s |%s %-7s %s| %-"+errPaddingStr+"s %s\n",
						timestamp.Load().(string),
						statusColor(c.Response().StatusCode(), colors), c.Response().StatusCode(), colors.Reset,
						data.Stop.Sub(data.Start).Round(time.Millisecond),
						c.IP(),
						methodColor(c.Method(), colors), c.Method(), colors.Reset,
						c.Path(),
						formatErr,
					),
				)
			} else {
				if chainErr != nil {
					formatErr = " | " + chainErr.Error()
				}
				_, _ = buf.WriteString( //nolint:errcheck // This will never fail
					fmt.Sprintf("%s | %3d | %7v | %15s | %-7s | %-"+errPaddingStr+"s %s\n",
						timestamp.Load().(string),
						c.Response().StatusCode(),
						data.Stop.Sub(data.Start).Round(time.Millisecond),
						c.IP(),
						c.Method(),
						c.Path(),
						formatErr,
					),
				)
			}

			// Write buffer to output
			_, _ = cfg.Output.Write(buf.Bytes()) //nolint:errcheck // This will never fail

			if cfg.Done != nil {
				cfg.Done(c, buf.Bytes())
			}

			// Put buffer back to pool
			bytebufferpool.Put(buf)

			// End chain
			return nil
		}

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my suggestion prior to opening this one.
• I understand that improperly formatted feature requests may be closed without explanation.

[brunodmartins]

This whole block of code showed on the snippet was removed on #2730