Check for bad todos

[WhyNotHugo]

I'd like to implement a check, report and repair command to do things like:

• Detect naive datetimes
• Detect missing timezones
• Scan for todos which fail to load.
• Find duplicate UIDs
• Etc.

The end goal is to:

• Have check to inform the user of anything broken.
• Have repair to attempt to fix fixable issues (eg: missing timezone, duplicate UIDs).
• Have report to generate a copy-pasteable report that users can provide for an issue.

[untitaker]

There's a certain overlap here, vdirsyncer can already fix duplicate UIDs. It also refuses to sync storages with duplicate UIDs.

I think check should happen at every start of todoman, i.e. warn every time about broken things.

report sounds nice in theory, though I'm unsure how you want to do automatic anonymization of user data.