APIv4 DELETE /users/{user_id}/posts/{post_id}/reactions/name (#6117)

* APIv4 DELETE /users/{user_id}/posts/{post_id}/reactions/name

* updated v3 deleteReaction endpoint

* update parameter of app.DeleteReactionForPost()

* update utils.IsValidAlphaNum, add utils.IsValidAlphaNumHyphenUnderscore, and add related tests

model/team.go

@@ -233,7 +233,7 @@ func IsReservedTeamName(s string) bool {
 
 func IsValidTeamName(s string) bool {
 
-	if !IsValidAlphaNum(s, false) {
+	if !IsValidAlphaNum(s) {
 		return false
 	}