[SWIFT 4] BigDecimal support in Swift4Codegen not available.

Description

Swift4Codegen.java does not have type mapping for bigdecimal. Even if we add the below line

typeMapping.put("bigdecimal", "Double");

in Swift4Codegen.java and compile the jar and run it. it gives the below error

[main] WARN io.swagger.util.PropertyDeserializer - no property from bigdecimal, null, {ENUM=null, TITLE=null, DESCRIPTION=null, DEFAULT=null, PATTERN=null, DESCRIMINATOR=null, MIN_ITEMS=null, MAX_ITEMS=null, MIN_PROPERTIES=null, MAX_PROPERTIES=null, MIN_LENGTH=null, MAX_LENGTH=null, MINIMUM=null, MAXIMUM=null, EXCLUSIVE_MINIMUM=null, EXCLUSIVE_MAXIMUM=null, UNIQUE_ITEMS=null, EXAMPLE=null, TYPE=bigdecimal, FORMAT=null, READ_ONLY=null, VENDOR_EXTENSIONS={}, MULTIPLE_OF=null}

Swagger-codegen version

master code

Swagger declaration file content or url

swagger: "2.0"
info:
  description: "Testing the swagger YAML to swift 4"
  version: "1.0.0"
  title: "testing swift"
  contact:
    email: "vpmsureshkumar@gmail.com"
  license:
    name: "sample code"
host: "localhost:8080"
basePath: "/v2"
schemes:
- "http"
paths:
  /user:
    put:
      summary: "Updated user"
      description: "This can only be done by the logged in user."
      operationId: "updateUser"
      produces:
      - "application/json"
      parameters:
      - in: "body"
        name: "user"
        description: "Updated user object"
        required: true
        schema:
          $ref: "#/definitions/User"
      responses:
        400:
          description: "Invalid user supplied"
        404:
          description: "User not found"
definitions:
  User:
    type: "object"
    properties:
      desk:
        type: "bigdecimal"
      firstName:
        type: "string"
        

Command line used for generation

swagger-codegen generate -i swagger_1.yaml -l swift4

Steps to reproduce

always

Related issues/PRs

Suggest a fix/enhancement

if I change my yaml and convert the
definitions:
User:
type: "object"
properties:
desk:
type: "number"
firstName:
type: "string"

then it works fine.
please tell me if 'number' should be used for big decimal in yaml? so that it gets converted to Double in swift?

Start with Swift4Codegen.java and the supplied Swagger YAML, then run the shown swagger-codegen generate -i swagger_1.yaml -l swift4 command to trace how bigdecimal is handled before Swift type mapping. Confirm whether the supported Swagger type should be number or whether bigdecimal needs explicit support, and verify that generation completes with the expected Swift representation.