PLT-1800 Load server side locale from the config.json (#3092)

* PLT-1800 Load server side locale from the config.json

* Add support for locales with country specifics

* Fix localization on served locale file as plain/text

model/config.go

@@ -204,20 +204,27 @@ type ComplianceSettings struct {
 	EnableDaily *bool
 }
 
+type LocalizationSettings struct {
+	DefaultServerLocale *string
+	DefaultClientLocale *string
+	AvailableLocales    *string
+}
+
 type Config struct {
-	ServiceSettings    ServiceSettings
-	TeamSettings       TeamSettings
-	SqlSettings        SqlSettings
-	LogSettings        LogSettings
-	FileSettings       FileSettings
-	EmailSettings      EmailSettings
-	RateLimitSettings  RateLimitSettings
-	PrivacySettings    PrivacySettings
-	SupportSettings    SupportSettings
-	GitLabSettings     SSOSettings
-	GoogleSettings     SSOSettings
-	LdapSettings       LdapSettings
-	ComplianceSettings ComplianceSettings
+	ServiceSettings      ServiceSettings
+	TeamSettings         TeamSettings
+	SqlSettings          SqlSettings
+	LogSettings          LogSettings
+	FileSettings         FileSettings
+	EmailSettings        EmailSettings
+	RateLimitSettings    RateLimitSettings
+	PrivacySettings      PrivacySettings
+	SupportSettings      SupportSettings
+	GitLabSettings       SSOSettings
+	GoogleSettings       SSOSettings
+	LdapSettings         LdapSettings
+	ComplianceSettings   ComplianceSettings
+	LocalizationSettings LocalizationSettings
 }
 
 func (o *Config) ToJson() string {
@@ -513,6 +520,21 @@ func (o *Config) SetDefaults() {
 		o.LdapSettings.NicknameAttribute = new(string)
 		*o.LdapSettings.NicknameAttribute = ""
 	}
+
+	if o.LocalizationSettings.DefaultServerLocale == nil {
+		o.LocalizationSettings.DefaultServerLocale = new(string)
+		*o.LocalizationSettings.DefaultServerLocale = DEFAULT_LOCALE
+	}
+
+	if o.LocalizationSettings.DefaultClientLocale == nil {
+		o.LocalizationSettings.DefaultClientLocale = new(string)
+		*o.LocalizationSettings.DefaultClientLocale = DEFAULT_LOCALE
+	}
+
+	if o.LocalizationSettings.AvailableLocales == nil {
+		o.LocalizationSettings.AvailableLocales = new(string)
+		*o.LocalizationSettings.AvailableLocales = *o.LocalizationSettings.DefaultClientLocale
+	}
 }
 
 func (o *Config) IsValid() *AppError {

model/user.go

@@ -136,7 +136,6 @@ func (u *User) PreSave() {
 
 	u.Username = strings.ToLower(u.Username)
 	u.Email = strings.ToLower(u.Email)
-	u.Locale = strings.ToLower(u.Locale)
 
 	u.CreateAt = GetMillis()
 	u.UpdateAt = u.CreateAt
@@ -166,7 +165,6 @@ func (u *User) PreSave() {
 func (u *User) PreUpdate() {
 	u.Username = strings.ToLower(u.Username)
 	u.Email = strings.ToLower(u.Email)
-	u.Locale = strings.ToLower(u.Locale)
 	u.UpdateAt = GetMillis()
 
 	if u.AuthData != nil && *u.AuthData == "" {