IdP-initiated SSO with SAML

Hanko's SAML implementation is now able to handle Identity provider (IdP) initiated login requests. This is a key feature for B2B customers that require their own IdP to handle authentication to apps that use Hanko. Now, those B2B users can access apps that use Hanko via their "App directories" or "App launchers" (e.g. Entra, Google Workspace, Okta) and initiate the authentication flow right from there. The existing SAML flow (SP-initiated SSO) can continue to be used.