Mocks should respect string length restrictions

[benwaffle]

When you write { "name": "currency", "minimum": 3, "maximum": 3 }, the mock clients should only generate strings of length 3.

One solution is that Factories.randomString() could take an optional length parameter, and then the factory will pass the minimum length.

[mbryzek]

this is a good idea that we should do asap - should be a small change - want to take a stab?

[mkows]

@benwaffle please see my proof of concept #515. Should do the job.

Please comment on TODO and comments in code.

[mkows]

Please take a brief look when you get a chance @benwaffle @mbryzek @gheine

Run locally, and for https://app.apibuilder.io/michal/playground-api/0.0.2-dev#model-error
(raw: http://localhost:9000/michal/playground-api/0.0.2-dev/original)
api.json:

    "error": {
      "fields": [
        {
          "name": "code",
          "type": "integer"
        },
        {
          "name": "message",
          "type": "string",
          "maximum": 12
        },
        {
          "name": "message_code",
          "type": "string",
          "minimum": 2,
          "maximum": 2
        },
        {
          "name": "message_lengthy",
          "type": "string",
          "minimum": 30
        },
        {
          "name": "details",
          "type": "string",
          "required": false
        }
      ]
    },
    "healthcheck": {
      "fields": [
        {
          "name": "status",
          "type": "string",
          "example": "healthy",
          "minimum": 3
        },
        {
          "name": "created_at",
          "type": "date-time-iso8601",
          "example": "2014-04-29T11:56:52Z"
        }
      ]
    }

the output is:
Play 2.6:

  object Factories {

    def randomString(length: Int = 24): String = {
      _root_.scala.util.Random.alphanumeric.take(length).mkString
    }

    def makeError(): io.github.mkows.playground.api.v0.models.Error = io.github.mkows.playground.api.v0.models.Error(
      code = 1,
      message = Factories.randomString(12),
      messageCode = Factories.randomString(2),
      messageLengthy = Factories.randomString(30),
      details = None
    )

    def makeHealthcheck(): io.github.mkows.playground.api.v0.models.Healthcheck = io.github.mkows.playground.api.v0.models.Healthcheck(
      status = Factories.randomString(24),
      createdAt = org.joda.time.DateTime.now
    )

Http4s 0.20

  object Factories {

    def randomString(length: Int = 24): String = {
      _root_.scala.util.Random.alphanumeric.take(length).mkString
    }

    def makeError(): io.github.mkows.playground.api.v0.models.Error = io.github.mkows.playground.api.v0.models.Error(
      code = 1,
      message = Factories.randomString(12),
      messageCode = Factories.randomString(2),
      messageLengthy = Factories.randomString(30),
      details = None
    )

    def makeHealthcheck(): io.github.mkows.playground.api.v0.models.Healthcheck = io.github.mkows.playground.api.v0.models.Healthcheck(
      status = Factories.randomString(24),
      createdAt = java.time.Instant.now
    )

PR: #515 (with some TODO comments -- mostly around supporting randomString(length = Int.MaxValue | Long.MaxValue) 😨 which should be rejected).