PLT-3143 Added serverside code for custom Emoji (#3311)

* Added model objects for emoji

* Added database tables for emoji

* Added settings for custom emoji

* Added serverside APIs and unit tests for custom emoji

* Added additional validation to catch duplicate emoji names earlier on

* Added additional validation to prevent users from adding emoji as another user

utils/config.go

@@ -251,6 +251,9 @@ func getClientConfig(c *model.Config) map[string]string {
 	props["AvailableLocales"] = *c.LocalizationSettings.AvailableLocales
 	props["SQLDriverName"] = c.SqlSettings.DriverName
 
+	props["EnableCustomEmoji"] = strconv.FormatBool(*c.ServiceSettings.EnableCustomEmoji)
+	props["RestrictCustomEmojiCreation"] = *c.ServiceSettings.RestrictCustomEmojiCreation
+
 	if IsLicensed {
 		if *License.Features.CustomBrand {
 			props["EnableCustomBrand"] = strconv.FormatBool(*c.TeamSettings.EnableCustomBrand)