[Typescript] add missing type mapping

[macjohnny]

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Description of the PR

Adds a missing type mapping
fixes #957

cc @TiFu (2017/07) @taxpon (2017/07) @sebastianhaas (2017/07) @kenisteward (2017/07) @Vrolijkx (2017/09)

[macjohnny]

tested with the following definition

swagger: '2.0'
info:
  description: Test
  version: 1.0.0
  title: Test
host: localhost:8080
basePath: /v1
schemes:
  - http

# Path API Definitions
paths:
  /administration/stammdaten:
    post:
      consumes:
      - application/json
      parameters:
      - in: body
        name: body
        schema:
          type: object
          additionalProperties:
            type: object
            properties:
              code:
                type: integer
              text:
                type: string
      produces:
      - application/json
      responses:
        200:
          description: 'Successful operation'

# Data models
definitions:

  Stammdaten:
    type: object

    properties:

      modelMap:
        type: object
        additionalProperties:
          type: object
          properties:
            code:
              type: integer
            text:
              type: string

and configuration

{
  "supportES6": true,
  "providedInRoot": "true",
  "modelSuffix": "MySuffix",
  "serviceSuffix": "MySuffix",
  "ngVersion": "6.1.4"
}

to produce

import { StammdatenModelMapMySuffix } from './stammdatenModelMap';

export interface StammdatenMySuffix { 
    modelMap?: { [key: string]: StammdatenModelMapMySuffix; };
}

and

export interface StammdatenModelMapMySuffix { 
    code?: number;
    text?: string;
}

and

import { Inject, Injectable, Optional }                      from '@angular/core';
import { HttpClient, HttpHeaders, HttpParams,
         HttpResponse, HttpEvent }                           from '@angular/common/http';
import { CustomHttpUrlEncodingCodec }                        from '../encoder';

import { Observable }                                        from 'rxjs';


import { BASE_PATH, COLLECTION_FORMATS }                     from '../variables';
import { Configuration }                                     from '../configuration';


@Injectable({
  providedIn: 'root'
})
export class DefaultMySuffix {
...
}

[macjohnny]

@wing328 could you please review and merge this? it is a tiny change

[wing328]

LGTM

[wing328]

@macjohnny thanks again for the PR, which is included in the v3.3.0 minor release: https://twitter.com/oas_generator/status/1046941449609068544