[BUG] [jaxrs-spec] Invalid class name is genereated when there is a number in the name

Description

When type name has a number in it for example A2ZPet the generated class name is A2zPet while in a file named A2ZPet also the refs created are A2ZPet.

openapi-generator version

openapi-generator-cli 6.5.0
  commit : 7417432
  built  : 2023-04-01T07:15:47Z
  source : https://github.com/openapitools/openapi-generator
  docs   : https://openapi-generator.tech/

OpenAPI declaration file content or url

openapi: 3.0.2
info:
  title: PetManager
  version: '2022-01-01'
paths:
  /data/pets:
    get:
      operationId: GetPets
      responses:
        '200':
          description: GetPets 200 response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/GetPetsResponseContent'
components:
  schemas:
    APet:
      type: object
      properties:
        id:
          type: number
    GetPetsResponseContent:
      type: object
      properties:
        error:
          type: string
        result:
          $ref: '#/components/schemas/PetsResult'
    A2ZPet:
      type: object
      properties:
        id:
          type: number
    PetListItem:
      oneOf:
        - type: object
          title: aPet
          properties:
            aPet:
              $ref: '#/components/schemas/APet'
          required:
            - aPet
        - type: object
          title: a2zPet
          properties:
            a2zPet:
              $ref: '#/components/schemas/A2ZPet'
          required:
            - a2zPet
    PetsResult:
      type: object
      properties:
        type:
          type: string
        pets:
          type: array
          items:
            $ref: '#/components/schemas/PetListItem'

Command line used for generation

openapi-generator generate -i spec.yaml -g jaxrs-spec -o .

Steps to reproduce

Save the above spec in spec.yaml and run the above command.

Start with spec.yaml and run the documented openapi-generator command using the jaxrs-spec generator. Compare the generated A2ZPet-related class, file, and references; done means the generated class name matches the schema and referenced names consistently.