DefaultSecurityService should use RolesFinder

[sdelamo]

I agree with you @dstepanov DefaultSecurityServiceshould use RolesFinder. Could you check this PR and let me know if it aligns with what you are looking for.

Aside: I've created a RolesFinder::hasAnyRequiredRoles so that we have a single place which can be override to support for example Case Insensitive roles

[dstepanov]

Looks good, maybe it would be better to have RolesFinder::hasAnyRequiredRoles(Claims claims, requiredRoles)
so this code can be reduced to one call:

.map(rolesFinder::findInClaims)
.map(grantedRoles -> rolesFinder.hasAnyRequiredRoles(Collections.singletonList(role), grantedRoles))

BTW: Can you please take a look at #289? I can redo PR for master.

[sdelamo]

I've created a RolesFinder::hasAnyRequiredRoles(List<String> requiredRoles, Authentication authentication) to simplify things further.