[BUG][Kotlin][Spring] Test won't compile when parameter is required

Created by: Zomzog

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Required parameter generate tests that won't compile

openapi-generator version

5.2.0

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: Repro
  version: '1.0'
  contact:
    name: Vlad
    email: vlad@vlad.vlad
paths:
  '/getSome/{what}':
    parameters:
      - $ref: '#/components/parameters/repro'
      - $ref: '#/components/parameters/what'
    get:
      responses:
        '200':
          description: OK
components:
  parameters:
    repro:
      name: X-Repro
      in: header
      required: true
      schema:
        $ref: '#/components/schemas/Id'
    what:
      name: what
      in: path
      required: true
      schema:
        $ref: '#/components/schemas/Id'
  schemas:
    Id:
      type: string
      pattern: '^[0-9]+$'
      minLength: 1
      maxLength: 5

Related issues/PRs

Discovered while fixing #10702 (closed)

Suggest a fix

Replace null by TODO() and handle ? like in other templates