[REQ][validate] Warn for validation keyword type mismatch

Created by: kevinoid

Currently validate does not warn if JSON Schema validation keywords are applied to schemas with types for which the validation keyword has no effect. For example:

openapi: '3.0.3'
info:
  title: Incorrect validation keyword example
  version: '1.0.0'
components:
  schemas:
    Vector3:
      type: array
      items:
        type: number
      maxLength: 3
      minLength: 3
paths:
  /location:
    get:
      operationId: getLocation
      responses:
        '200':
          description: Success
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Vector3'

openapi-generator-cli.jar validate -i openapi.yaml produces:

Validating spec (openapi.yaml)
No validation issues detected.

However, maxLength/minLength validate the length of strings and have no effect on Vector3, which has type: array. The author likely intended to use maxItems/minItems.

Is there any chance you'd consider producing a warning for such cases?

Thanks for considering, Kevin