Add flash message after an account has been successfully activated (#4510)

* added new locale text

options/locale/locale_en-US.ini

@@ -203,6 +203,7 @@ sign_up_now = Need an account? Register now.
 confirmation_mail_sent_prompt = A new confirmation email has been sent to <b>%s</b>. Please check your inbox within the next %s to complete the registration process.
 reset_password_mail_sent_prompt = A confirmation email has been sent to <b>%s</b>. Please check your inbox within the next %s to complete the password reset process.
 active_your_account = Activate Your Account
+account_activated = Account has been activated
 prohibit_login = Sign In Prohibited
 prohibit_login_desc = Your account is prohibited to sign in, please contact your site administrator.
 resent_limit_prompt = You have already requested an activation email recently. Please wait 3 minutes and try again.

routers/user/auth.go

@@ -1035,6 +1035,7 @@ func Activate(ctx *context.Context) {
 
 		ctx.Session.Set("uid", user.ID)
 		ctx.Session.Set("uname", user.Name)
+		ctx.Flash.Success(ctx.Tr("auth.account_activated"))
 		ctx.Redirect(setting.AppSubURL + "/")
 		return
 	}