Use a different SAML IdP for SAML Cypress tests to avoid dependency on outdated node package

[cwperks]

Is your feature request related to a problem?

Currently, when performing SAML tests, the security-dashboards-plugin spins up a node-based SAML IdP based on the saml-idp node package. The last published version of this package was 5 years ago and it gets flagged by scanners as having transitive dependencies with vulnerabilities.

Before running the SAML tests, this repo has a prescript to run this IdP which spins up a separate process hosted at http://localhost:7000. When running tests with SAML the application redirects out of OSD (http://localhost:5601) to the IdP (http://localhost:7000) and is redirected back into OSD after successful authentication.

We should either contribute a fix upstream or replace the node-based IdP all together with something like SimpleSAML.

When testing the OIDC login flow, this repo uses Keycloak, it may be possible to run Keycloak as a SAML provider as well which could be another avenue looked into.