What Koala extension does this refer to (if applicable)
IntroCog, but also all Extensions

Is your feature request related to a problem? Please describe.
Many people are put off by Koala DMing all users upon joining the server. This solution needs to allow Koala to legally run with an option not to DM all users by default, and have options to remove it in every cog that currently does.

Describe the solution you'd like

1. Remove Welcome message requirement, make it instead optional if given by the server with an updated embed & image. (if empty/ currently unassigned, don't send)
2. Review all current commands for when personally identifying info is given, in which case the user is given brief info on data storage and a link to our privacy document
3. Make Devs aware of best practices for including these notifications
4. Create a k!setup command that is required before any data on a server is stored (making most commands inaccessible until k!setup is run) in which the admin will accept the GDPR document for storing data about their discord server (doesn't apply for individual data e.g. emails, that still needs to be sent to those individuals too)
5. Add an option to not DM by verify when people join

Describe alternatives you've considered
Only DM people when taking in data from them, e.g. a confirmation of storing their email when using k!verify.

Additional context
As well as linking to http://legal.koalabot.uk the user should also be alerted to what type of data is being stored (e.g. UserID and Email)