closes#9587
- when `useNullAsDefault` was invented in knex 0.10, it was a breaking change, that update/insert etc no longer set's null as default if a field is missing
- at this time we thought it only affects our test env, because the test generator doesn't generate all fields
- but turned out the importer is affected as well e.g. you import a post with missing fields
- the importer doesn't iterate over all fields and checks if the field is present or not
- as this only happens with SQlite3, we should enable `useNullAsDefault` by default
- you can still disable this option if you want, but not recommended
- the reason why knex added this breaking change was that some applications want "undefined" as value
- this is not the case in Ghost, so it's fine to make use of the default null behaviour
issues #6406#6399
- all dates are stored as UTC with this commit
- use moment.tz.setDefault('UTC')
- add migration file to recalculate local datetimes to UTC
- store all dates in same format into our three supported databases
- add option to remeber migrations inside settings (core)
- support DST offset for migration
- ensure we force UTC in test env
- run whole migration as transaction
- extend: Settings.findOne function
refs #6623
- automatically set useNullAsDefault to false for sqlite3 so that we don't get a warning
- we should *not* be relying on the behaviour of interpretting undefined anywhere, so it is correct that an error should be output if this happens so that we can fix the bad behaviour
