Referential Constraints for Datetime Types

[dluftspring]

Required Functionality A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

As a user generating data I would like to be able to impose inequality constraints between two datetime fields for the same record in a JSON array.

For example

"created_at": {
  "type": "date_time"
},

"last_login": {
   "type": "date_time"
   "begin": min(<collection>.created_at) 
}

Proposed Solution What you would see the solution looking like. If you have no idea - just leave empty.

Use case Some background on the usecase that this feature would address.