Attachment reference regular expression constraint

[OldSneerJaw]

Feature Request

Description

Add a new constraint to the attachmentReference validation type that specifies a regular expression pattern that the corresponding attachment's filename must match. Should take precedence over the document-wide attachmentConstraints.filenameRegexPattern constraint.

Examples

With a static value:

myDoc1: {
  typeFilter: simpleTypeFilter,
  authorizedRoles: { write: 'write' },
  allowAttachments: true,
  propertyValidators: {
    myAttachmentProperty: {
      type: 'attachmentReference',
      regexPattern: /^[a-z]+-\d{1,4}\.xml$/
    }
  }
}

And with a dynamic value:

myDoc2: {
  typeFilter: simpleTypeFilter,
  authorizedRoles: { write: 'write' },
  allowAttachments: true,
  propertyValidators: {
    myAttachmentProperty: {
      type: 'attachmentReference',
      regexPattern: function(doc, oldDoc, value, oldValue) {
        return new RegExp('^' + doc._id + '-\\d{2}\\.pdf$');
      }
    }
  }
}

[dkichler]

Satisfied by #28