This commit adds a check that runs regularly as per
2d68e5d942 which tests the
credentials of groups with SMTP or IMAP enabled. If any issues
are found with those credentials a high priority problem is added to the
admin dashboard.
This commit also formats the admin dashboard differently if
there are high priority problems, bringing them to the top of
the list and highlighting them.
The problem will be cleared if the issue is fixed before the next
problem check, or if the group's settings are updated with a valid
credential.
This commit introduces scheduled problem checks for the admin dashboard, which are long running or otherwise cumbersome problem checks that will be run every 10 minutes rather than every time the dashboard is loaded. If these scheduled checks add a problem, the problem will remain until it is cleared or until the scheduled job runs again.
An example of a check that should be scheduled is validating credentials against an external provider.
This commit also introduces the concept of a `priority` to the problems generated by `AdminDashboardData` and the scheduled checks. This is `low` by default, and can be set to `high`, but this commit does not change any part of the UI with this information, only adds a CSS class.
I will be making a follow up PR to check group SMTP credentials.
