Support MySQL 8

[SingingBush]

While doing #227 / #228, I setup some MySQL 8 testing which currently fail. There's already issue #189 which will need resolving to support v8 but I suspect there's more issues to tackle as well.

It's worth having some labels configured for:

• mysql 8
• mysql 5.7
• mariadb 10

So that if a problem is db specific it can be highlighted. It will also make it easy to filter issues based on db type.

Perhaps use this ticket as a parent ticket for any other issues that need resolving so that MySQL 8 can be supported

[schveiguy]

It's worth having some labels

Added