Rewrite logger system (#24726)

## ⚠️ Breaking

The `log.<mode>.<logger>` style config has been dropped. If you used it,
please check the new config manual & app.example.ini to make your
instance output logs as expected.

Although many legacy options still work, it's encouraged to upgrade to
the new options.

The SMTP logger is deleted because SMTP is not suitable to collect logs.

If you have manually configured Gitea log options, please confirm the
logger system works as expected after upgrading.

## Description

Close #12082 and maybe more log-related issues, resolve some related
FIXMEs in old code (which seems unfixable before)

Just like rewriting queue #24505 : make code maintainable, clear legacy
bugs, and add the ability to support more writers (eg: JSON, structured
log)

There is a new document (with examples): `logging-config.en-us.md`

This PR is safer than the queue rewriting, because it's just for
logging, it won't break other logic.

## The old problems

The logging system is quite old and difficult to maintain:
* Unclear concepts: Logger, NamedLogger, MultiChannelledLogger,
SubLogger, EventLogger, WriterLogger etc
* Some code is diffuclt to konw whether it is right:
`log.DelNamedLogger("console")` vs `log.DelNamedLogger(log.DEFAULT)` vs
`log.DelLogger("console")`
* The old system heavily depends on ini config system, it's difficult to
create new logger for different purpose, and it's very fragile.
* The "color" trick is difficult to use and read, many colors are
unnecessary, and in the future structured log could help
* It's difficult to add other log formats, eg: JSON format
* The log outputer doesn't have full control of its goroutine, it's
difficult to make outputer have advanced behaviors
* The logs could be lost in some cases: eg: no Fatal error when using
CLI.
* Config options are passed by JSON, which is quite fragile.
* INI package makes the KEY in `[log]` section visible in `[log.sub1]`
and `[log.sub1.subA]`, this behavior is quite fragile and would cause
more unclear problems, and there is no strong requirement to support
`log.<mode>.<logger>` syntax.


## The new design

See `logger.go` for documents.


## Screenshot

<details>


![image](https://github.com/go-gitea/gitea/assets/2114189/4462d713-ba39-41f5-bb08-de912e67e1ff)


![image](https://github.com/go-gitea/gitea/assets/2114189/b188035e-f691-428b-8b2d-ff7b2199b2f9)


![image](https://github.com/go-gitea/gitea/assets/2114189/132e9745-1c3b-4e00-9e0d-15eaea495dee)

</details>

## TODO

* [x] add some new tests
* [x] fix some tests
* [x] test some sub-commands (manually ....)

---------

Co-authored-by: Jason Song <i@wolfogre.com>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: Giteabot <teabot@gitea.io>

modules/log/logger.go

@@ -1,141 +1,50 @@
-// Copyright 2019 The Gitea Authors. All rights reserved.
+// Copyright 2023 The Gitea Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
+// Package log provides logging capabilities for Gitea.
+// Concepts:
+//
+// * Logger: a Logger provides logging functions and dispatches log events to all its writers
+//
+// * EventWriter: written log Event to a destination (eg: file, console)
+//   - EventWriterBase: the base struct of a writer, it contains common fields and functions for all writers
+//   - WriterType: the type name of a writer, eg: console, file
+//   - WriterName: aka Mode Name in document, the name of a writer instance, it's usually defined by the config file.
+//     It is called "mode name" because old code use MODE as config key, to keep compatibility, keep this concept.
+//
+// * WriterMode: the common options for all writers, eg: log level.
+//   - WriterConsoleOption and others: the specified options for a writer, eg: file path, remote address.
+//
+// Call graph:
+// -> log.Info()
+// -> LoggerImpl.Log()
+// -> LoggerImpl.SendLogEvent, then the event goes into writer's goroutines
+// -> EventWriter.Run() handles the events
 package log
 
-import "os"
-
-// Logger is the basic interface for logging
-type Logger interface {
-	LevelLogger
-	Trace(format string, v ...interface{})
-	IsTrace() bool
-	Debug(format string, v ...interface{})
-	IsDebug() bool
-	Info(format string, v ...interface{})
-	IsInfo() bool
-	Warn(format string, v ...interface{})
-	IsWarn() bool
-	Error(format string, v ...interface{})
-	ErrorWithSkip(skip int, format string, v ...interface{})
-	IsError() bool
-	Critical(format string, v ...interface{})
-	CriticalWithSkip(skip int, format string, v ...interface{})
-	IsCritical() bool
-	Fatal(format string, v ...interface{})
-	FatalWithSkip(skip int, format string, v ...interface{})
-	IsFatal() bool
-}
-
-// LevelLogger is the simplest logging interface
-type LevelLogger interface {
-	Flush()
-	Close()
+// BaseLogger provides the basic logging functions
+type BaseLogger interface {
+	Log(skip int, level Level, format string, v ...any)
 	GetLevel() Level
-	Log(skip int, level Level, format string, v ...interface{}) error
 }
 
-// SettableLogger is the interface of loggers which have subloggers
-type SettableLogger interface {
-	SetLogger(name, provider, config string) error
-	DelLogger(name string) (bool, error)
+// LevelLogger provides level-related logging functions
+type LevelLogger interface {
+	LevelEnabled(level Level) bool
+
+	Trace(format string, v ...any)
+	Debug(format string, v ...any)
+	Info(format string, v ...any)
+	Warn(format string, v ...any)
+	Error(format string, v ...any)
+	Critical(format string, v ...any)
 }
 
-// StacktraceLogger is a logger that can log stacktraces
-type StacktraceLogger interface {
-	GetStacktraceLevel() Level
-}
-
-// LevelLoggerLogger wraps a LevelLogger as a Logger
-type LevelLoggerLogger struct {
+type Logger interface {
+	BaseLogger
 	LevelLogger
 }
 
-// Trace records trace log
-func (l *LevelLoggerLogger) Trace(format string, v ...interface{}) {
-	l.Log(1, TRACE, format, v...) //nolint:errcheck
-}
-
-// IsTrace returns true if the logger is TRACE
-func (l *LevelLoggerLogger) IsTrace() bool {
-	return l.GetLevel() <= TRACE
-}
-
-// Debug records debug log
-func (l *LevelLoggerLogger) Debug(format string, v ...interface{}) {
-	l.Log(1, DEBUG, format, v...) //nolint:errcheck
-}
-
-// IsDebug returns true if the logger is DEBUG
-func (l *LevelLoggerLogger) IsDebug() bool {
-	return l.GetLevel() <= DEBUG
-}
-
-// Info records information log
-func (l *LevelLoggerLogger) Info(format string, v ...interface{}) {
-	l.Log(1, INFO, format, v...) //nolint:errcheck
-}
-
-// IsInfo returns true if the logger is INFO
-func (l *LevelLoggerLogger) IsInfo() bool {
-	return l.GetLevel() <= INFO
-}
-
-// Warn records warning log
-func (l *LevelLoggerLogger) Warn(format string, v ...interface{}) {
-	l.Log(1, WARN, format, v...) //nolint:errcheck
-}
-
-// IsWarn returns true if the logger is WARN
-func (l *LevelLoggerLogger) IsWarn() bool {
-	return l.GetLevel() <= WARN
-}
-
-// Error records error log
-func (l *LevelLoggerLogger) Error(format string, v ...interface{}) {
-	l.Log(1, ERROR, format, v...) //nolint:errcheck
-}
-
-// ErrorWithSkip records error log from "skip" calls back from this function
-func (l *LevelLoggerLogger) ErrorWithSkip(skip int, format string, v ...interface{}) {
-	l.Log(skip+1, ERROR, format, v...) //nolint:errcheck
-}
-
-// IsError returns true if the logger is ERROR
-func (l *LevelLoggerLogger) IsError() bool {
-	return l.GetLevel() <= ERROR
-}
-
-// Critical records critical log
-func (l *LevelLoggerLogger) Critical(format string, v ...interface{}) {
-	l.Log(1, CRITICAL, format, v...) //nolint:errcheck
-}
-
-// CriticalWithSkip records critical log from "skip" calls back from this function
-func (l *LevelLoggerLogger) CriticalWithSkip(skip int, format string, v ...interface{}) {
-	l.Log(skip+1, CRITICAL, format, v...) //nolint:errcheck
-}
-
-// IsCritical returns true if the logger is CRITICAL
-func (l *LevelLoggerLogger) IsCritical() bool {
-	return l.GetLevel() <= CRITICAL
-}
-
-// Fatal records fatal log and exit the process
-func (l *LevelLoggerLogger) Fatal(format string, v ...interface{}) {
-	l.Log(1, FATAL, format, v...) //nolint:errcheck
-	l.Close()
-	os.Exit(1)
-}
-
-// FatalWithSkip records fatal log from "skip" calls back from this function and exits the process
-func (l *LevelLoggerLogger) FatalWithSkip(skip int, format string, v ...interface{}) {
-	l.Log(skip+1, FATAL, format, v...) //nolint:errcheck
-	l.Close()
-	os.Exit(1)
-}
-
-// IsFatal returns true if the logger is FATAL
-func (l *LevelLoggerLogger) IsFatal() bool {
-	return l.GetLevel() <= FATAL
+type LogStringer interface { //nolint:revive
+	LogString() string
 }