New setting: firstTimeResponseMessage

[Hector1801]

Default Value = none

When enabled, the bot would prioritize this setting over the regular responseMessage setting, as long as it's the first time of the user DMing the bot. This can be used to give the user a little introduction on what's the bot/server about, so that they know how to correctly interact with/in it, leaving the responseMessage setting to just let the user know that the bot managers have successfully received their message.

In future tickets created by the same user, the bot would send the regular responseMessage.