Support POJOs for request param mapping

[ashwini-desai]

Sample input:

paths:
  /pets:
    get:
      summary: get pets
      operationId: getPets
      tags:
        - pets
      requestBody:
        description: 'Fetch pets'
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/PaginationCommand"
      responses:
         '200':
           description: Expected response to a valid request
           content:
             application/json:
               schema:
                 type: array
                 items:
                   $ref: "#/components/schemas/Pet"
components:
   schemas:
      PaginationCommand:
          type: object
          required:
            - offset
            - limit
          properties:
            offset:
              type: integer
              format: int64
              minimum: 0
            limit:
              type: integer
              format: int64
              minimum: 10

Sample output:

Controller method -

     @Get(value = "/pets{?paginationCommand*}")
     fun showPetById(paginationCommand: PaginationCommand): HttpResponse<Pet> {
        ....
    }

PaginationCommand class -

data class PaginationCommand(val offset: Int = 0, val limit: Int = 10)

We should be able to take default values from yaml. Also, micronaut needs default values for POJOs mapped from requests, so will have to be made mandatory in apifi for request param models to be mapped as POJOs.