[MM-24391] Render icon_emoji names surrounded by colons in incoming webhooks (#15753)

app/post_metadata.go

@@ -81,6 +81,8 @@ func (a *App) OverrideIconURLIfEmoji(post *model.Post) {
 		return
 	}
 
+	emojiName = strings.ReplaceAll(emojiName, ":", "")
+
 	if emojiUrl, err := a.GetEmojiStaticUrl(emojiName); err == nil {
 		post.AddProp(model.POST_PROPS_OVERRIDE_ICON_URL, emojiUrl)
 	} else {