Add context cache as a request level cache (#22294)

To avoid duplicated load of the same data in an HTTP request, we can set
a context cache to do that. i.e. Some pages may load a user from a
database with the same id in different areas on the same page. But the
code is hidden in two different deep logic. How should we share the
user? As a result of this PR, now if both entry functions accept
`context.Context` as the first parameter and we just need to refactor
`GetUserByID` to reuse the user from the context cache. Then it will not
be loaded twice on an HTTP request.

But of course, sometimes we would like to reload an object from the
database, that's why `RemoveContextData` is also exposed.

The core context cache is here. It defines a new context
```go
type cacheContext struct {
	ctx  context.Context
	data map[any]map[any]any
        lock sync.RWMutex
}

var cacheContextKey = struct{}{}

func WithCacheContext(ctx context.Context) context.Context {
	return context.WithValue(ctx, cacheContextKey, &cacheContext{
		ctx:  ctx,
		data: make(map[any]map[any]any),
	})
}
```

Then you can use the below 4 methods to read/write/del the data within
the same context.

```go
func GetContextData(ctx context.Context, tp, key any) any
func SetContextData(ctx context.Context, tp, key, value any)
func RemoveContextData(ctx context.Context, tp, key any)
func GetWithContextCache[T any](ctx context.Context, cacheGroupKey string, cacheTargetID any, f func() (T, error)) (T, error)
```

Then let's take a look at how `system.GetString` implement it.

```go
func GetSetting(ctx context.Context, key string) (string, error) {
	return cache.GetWithContextCache(ctx, contextCacheKey, key, func() (string, error) {
		return cache.GetString(genSettingCacheKey(key), func() (string, error) {
			res, err := GetSettingNoCache(ctx, key)
			if err != nil {
				return "", err
			}
			return res.SettingValue, nil
		})
	})
}
```

First, it will check if context data include the setting object with the
key. If not, it will query from the global cache which may be memory or
a Redis cache. If not, it will get the object from the database. In the
end, if the object gets from the global cache or database, it will be
set into the context cache.

An object stored in the context cache will only be destroyed after the
context disappeared.

models/system/setting.go

@@ -80,8 +80,8 @@ func IsErrDataExpired(err error) bool {
 }
 
 // GetSettingNoCache returns specific setting without using the cache
-func GetSettingNoCache(key string) (*Setting, error) {
-	v, err := GetSettings([]string{key})
+func GetSettingNoCache(ctx context.Context, key string) (*Setting, error) {
+	v, err := GetSettings(ctx, []string{key})
 	if err != nil {
 		return nil, err
 	}
@@ -91,27 +91,31 @@ func GetSettingNoCache(key string) (*Setting, error) {
 	return v[strings.ToLower(key)], nil
 }
 
+const contextCacheKey = "system_setting"
+
 // GetSetting returns the setting value via the key
-func GetSetting(key string) (string, error) {
-	return cache.GetString(genSettingCacheKey(key), func() (string, error) {
-		res, err := GetSettingNoCache(key)
-		if err != nil {
-			return "", err
-		}
-		return res.SettingValue, nil
+func GetSetting(ctx context.Context, key string) (string, error) {
+	return cache.GetWithContextCache(ctx, contextCacheKey, key, func() (string, error) {
+		return cache.GetString(genSettingCacheKey(key), func() (string, error) {
+			res, err := GetSettingNoCache(ctx, key)
+			if err != nil {
+				return "", err
+			}
+			return res.SettingValue, nil
+		})
 	})
 }
 
 // GetSettingBool return bool value of setting,
 // none existing keys and errors are ignored and result in false
-func GetSettingBool(key string) bool {
-	s, _ := GetSetting(key)
+func GetSettingBool(ctx context.Context, key string) bool {
+	s, _ := GetSetting(ctx, key)
 	v, _ := strconv.ParseBool(s)
 	return v
 }
 
 // GetSettings returns specific settings
-func GetSettings(keys []string) (map[string]*Setting, error) {
+func GetSettings(ctx context.Context, keys []string) (map[string]*Setting, error) {
 	for i := 0; i < len(keys); i++ {
 		keys[i] = strings.ToLower(keys[i])
 	}
@@ -161,16 +165,17 @@ func GetAllSettings() (AllSettings, error) {
 }
 
 // DeleteSetting deletes a specific setting for a user
-func DeleteSetting(setting *Setting) error {
+func DeleteSetting(ctx context.Context, setting *Setting) error {
+	cache.RemoveContextData(ctx, contextCacheKey, setting.SettingKey)
 	cache.Remove(genSettingCacheKey(setting.SettingKey))
 	_, err := db.GetEngine(db.DefaultContext).Delete(setting)
 	return err
 }
 
-func SetSettingNoVersion(key, value string) error {
-	s, err := GetSettingNoCache(key)
+func SetSettingNoVersion(ctx context.Context, key, value string) error {
+	s, err := GetSettingNoCache(ctx, key)
 	if IsErrSettingIsNotExist(err) {
-		return SetSetting(&Setting{
+		return SetSetting(ctx, &Setting{
 			SettingKey:   key,
 			SettingValue: value,
 		})
@@ -179,11 +184,11 @@ func SetSettingNoVersion(key, value string) error {
 		return err
 	}
 	s.SettingValue = value
-	return SetSetting(s)
+	return SetSetting(ctx, s)
 }
 
 // SetSetting updates a users' setting for a specific key
-func SetSetting(setting *Setting) error {
+func SetSetting(ctx context.Context, setting *Setting) error {
 	if err := upsertSettingValue(strings.ToLower(setting.SettingKey), setting.SettingValue, setting.Version); err != nil {
 		return err
 	}
@@ -192,9 +197,11 @@ func SetSetting(setting *Setting) error {
 
 	cc := cache.GetCache()
 	if cc != nil {
-		return cc.Put(genSettingCacheKey(setting.SettingKey), setting.SettingValue, setting_module.CacheService.TTLSeconds())
+		if err := cc.Put(genSettingCacheKey(setting.SettingKey), setting.SettingValue, setting_module.CacheService.TTLSeconds()); err != nil {
+			return err
+		}
 	}
-
+	cache.SetContextData(ctx, contextCacheKey, setting.SettingKey, setting.SettingValue)
 	return nil
 }
 
@@ -244,7 +251,7 @@ var (
 
 func Init() error {
 	var disableGravatar bool
-	disableGravatarSetting, err := GetSettingNoCache(KeyPictureDisableGravatar)
+	disableGravatarSetting, err := GetSettingNoCache(db.DefaultContext, KeyPictureDisableGravatar)
 	if IsErrSettingIsNotExist(err) {
 		disableGravatar = setting_module.GetDefaultDisableGravatar()
 		disableGravatarSetting = &Setting{SettingValue: strconv.FormatBool(disableGravatar)}
@@ -255,7 +262,7 @@ func Init() error {
 	}
 
 	var enableFederatedAvatar bool
-	enableFederatedAvatarSetting, err := GetSettingNoCache(KeyPictureEnableFederatedAvatar)
+	enableFederatedAvatarSetting, err := GetSettingNoCache(db.DefaultContext, KeyPictureEnableFederatedAvatar)
 	if IsErrSettingIsNotExist(err) {
 		enableFederatedAvatar = setting_module.GetDefaultEnableFederatedAvatar(disableGravatar)
 		enableFederatedAvatarSetting = &Setting{SettingValue: strconv.FormatBool(enableFederatedAvatar)}
@@ -268,13 +275,13 @@ func Init() error {
 	if setting_module.OfflineMode {
 		disableGravatar = true
 		enableFederatedAvatar = false
-		if !GetSettingBool(KeyPictureDisableGravatar) {
-			if err := SetSettingNoVersion(KeyPictureDisableGravatar, "true"); err != nil {
+		if !GetSettingBool(db.DefaultContext, KeyPictureDisableGravatar) {
+			if err := SetSettingNoVersion(db.DefaultContext, KeyPictureDisableGravatar, "true"); err != nil {
 				return fmt.Errorf("Failed to set setting %q: %w", KeyPictureDisableGravatar, err)
 			}
 		}
-		if GetSettingBool(KeyPictureEnableFederatedAvatar) {
-			if err := SetSettingNoVersion(KeyPictureEnableFederatedAvatar, "false"); err != nil {
+		if GetSettingBool(db.DefaultContext, KeyPictureEnableFederatedAvatar) {
+			if err := SetSettingNoVersion(db.DefaultContext, KeyPictureEnableFederatedAvatar, "false"); err != nil {
 				return fmt.Errorf("Failed to set setting %q: %w", KeyPictureEnableFederatedAvatar, err)
 			}
 		}