Allow customization of redirect strategy in `CasAuthenticationEntrypoint`

[kakawait]

Expected Behavior

Allow more customization or inheritance for CasAuthenticationEntrypoint

Current Behavior

CasAuthenticationEntrypoint has final keyword on

@Override
public final void commence(final HttpServletRequest servletRequest, HttpServletResponse response,
		AuthenticationException authenticationException) throws IOException {
...
}

that prevent developer to change behavior.

If removing final isn't acceptable, otherwise allow changing hardcoded new DefaultRedirectStrategy() inside commence to allow injecting RedirectStrategy inside constructor

Context

Allow developer to apply different strategy without having copying CasAuthenticationEntrypoint, could resolve #3123 for example

---

I'm totally ok to propose a PR, but I'd like to get validation that is something acceptable

[rishiraj88]

Looks like a nice suggestion. Flexibility should be favoured unless there is a strong blocker.

[marcusdacoregio]

Thanks for the report @kakawait. I've repurposed the ticket to allow customization of the redirect strategy if you are okay with it.