[minDate] and [maxDate] validation returns misleading error description

[03byron]

Bug description:

Current [minDate] and [maxDate] validation returns misleading error description.

E.g. When [minDate] is set to today and you enter yesterday, validate() returns:

{'ngbDate': {requiredBefore: this.minDate}}

but it should be

{'ngbDate': {requiredAfter: this.minDate}}

Same applies for [maxDate]. When maxDate is set to today and you enter tomorrow you get:

{'ngbDate': {requiredAfter: this.maxDate}}

but it should be

{'ngbDate': {requiredBefore: this.maxDate}}

[maxokorokov]

Here is the stackblitz with the issue: https://stackblitz.com/edit/angular-snykrp.

date = 1 OCT 2018
minDate = 10 OCT 2018

I would expect the message to be along these lines:

• error: ngbDate is before 10 OCT 2010
• error: ngbDate must be after 10 OCT 2010

Currently it is:

• error: ngbDate required before 10 OCT 2010

FC: {
  "ngbDate": {
    "requiredBefore": {
      "year": 2018,
      "month": 10,
      "day": 10
    }
  }
}

I'd prefer to change requiredBefore to isBefore, mustBeAfter or simply beforeMinDate.

I'll leave @pkozlowski-opensource decide. And it is a breaking change.