Add integration test that searches for unnecessary SuppressWarning annotations in generated code

[spotlesscoder]

Overview of the feature request

Generated a new project with JHipster 8.6.0
The AccountResource.java has an unnecessary SuppressWarning here:

/**
     * {@code GET  /account} : get the current user.
     *
     * @param principal the current user; resolves to {@code null} if not authenticated.
     * @return the current user.
     * @throws AccountResourceException {@code 500 (Internal Server Error)} if the user couldn't be returned.
     */
    @GetMapping("/account")
    @SuppressWarnings("unchecked")
    public AdminUserDTO getAccount(Principal principal) {
        if (principal instanceof AbstractAuthenticationToken) {
            return userService.getUserFromAuthentication((AbstractAuthenticationToken) principal);
        } else {
            throw new AccountResourceException("User could not be found");
        }
    }

Motivation for or Use Case

Code should always be minimal

[spotlesscoder]

This fixes this one occurrence of the error.
The be safe that it does not occur again, the generator should have tests that every method is checked - at least check that the suppresswarning is not added when the method does not even have a "throws" declaration at all