[BUG] [typescript-angular] Incorrect OperationId Generated (starting with number)

Created by: karismann

Description

If you have an input declaration with an operationId starting with a number, the angular client generator doesn't transform this operationId and the code generated is incorrect with the TS1351 error :

"An identifier or keyword cannot immediately follow a numeric literal."

openapi-generator version

4.0.0-SNAPSHOT

OpenAPI declaration file content or url

  /another-fake/dummy:
    patch:
      tags:
        - $another-fake?
      summary: To test special tags
      description: To test special tags and operation ID starting with number
      operationId: '123_test_@#$%_special_tags'
      responses:
        '200':
          description: successful operation
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Client'
      requestBody:
        $ref: '#/components/requestBodies/Client'

generate

    public 123testSpecialTags(client: Client, observe?: 'body', reportProgress?: boolean): Observable<Client>;
    public 123testSpecialTags(client: Client, observe?: 'response', reportProgress?: boolean): Observable<HttpResponse<Client>>;
    public 123testSpecialTags(client: Client, observe?: 'events', reportProgress?: boolean): Observable<HttpEvent<Client>>;
...

instead of

    public _123testSpecialTags(client: Client, observe?: 'body', reportProgress?: boolean): Observable<Client>;
    public _123testSpecialTags(client: Client, observe?: 'response', reportProgress?: boolean): Observable<HttpResponse<Client>>;
    public _123testSpecialTags(client: Client, observe?: 'events', reportProgress?: boolean): Observable<HttpEvent<Client>>;
...

Suggest a fix

I will send a PR (i fixed the code locally)