20231222
20240127

#### references
https://learn.microsoft.com/en-us/dotnet/core/extensions/logging?tabs=command-line
https://learn.microsoft.com/en-us/samples/dotnet/samples/csharp-logging-fundamentals/
https://github.com/dotnet/samples/tree/main/core/logging

#### Log category
建立 ILogger 時, 需指定 category. 習慣上, category 建議命名為 namespace.class 如下例為 "Example.DefaultService":
ZLib 以 ProjectID 對應 category
namespace Example
{
    public class DefaultService : IService
    {
        private readonly ILogger<DefaultService> _logger;

        public DefaultService(ILogger<DefaultService> logger) =>
            _logger = logger;

        // ...
    }
}

#### LogLevel
LogLevel indicates the severity of the log and ranges from 0 to 6:
Trace = 0, Debug = 1, Information = 2, Warning = 3, Error = 4, Critical = 5, and None = 6.