Fix Map and byte[] for openapi

[Xerxekyran]

This pull requests contains two fixes when generating the openapi defintion using jooby-openapi:

Fix for Map:
According to https://swagger.io/docs/specification/data-models/dictionaries/ a map should be represented by a schema that has the type as well as an additionalProperties element with the type property set to the value property of the map.

So the following map

{
  "en": "English",
  "fr": "French"
}

should become the following schema:

type: object
  additionalProperties:
    type: string

Fix for byte[]:
There exists a special ByteArraySchema class that can be used in this case, as it produces the correct schema for it:

schema": {
  "type": "string",
  "format": "byte"
}

[Xerxekyran]

Shall I rebase the branch or fix the checkstyle problem that was introduced two days ago?

[jknack]

Fixed it. Thanks.

Build is running again