This PR allows us to validate the schema during test.
It also removes some cruft from the seed files and ensures only the required data is packaged and consumable, reducing the package weight somewhat.
* fix(seed): Simplify copy of lessons and remove need for image
* rework copy for account creation and login emails
* fix: Fixup email template and lock-file
the test fails if there is no space between @media and the parenthesis, even though it is possible to not have a space. Also it doesn't tell you that that is the problem, so it can make the person get stuck trying to figure out what they did wrong, when in fact they were right, like I was for half an hour until I came here to check the test =)
Some CSS tests were changed to regex tests while the CSS tests weren't
working on Firefox. Now that the original issue has been fixed, these
changes can be reverted.
Closes#15567
