This commit adds an OpenID Connect authentication realm to
elasticsearch. Elasticsearch (with the assistance of kibana or
another web component) acts as an OpenID Connect Relying
Party and supports the Authorization Code Grant and Implicit
flows as described in http://ela.st/oidc-spec. It adds support
for consuming and verifying signed ID Tokens, both RP
initiated and 3rd party initiated Single Sign on and RP
initiated signle logout.
It also adds an OpenID Connect Provider in the idp-fixture to
be used for the associated integration tests.
This is a backport of #40674
This change removes the use of hardcoded port values for the
idp-fixture in favor of the mapped ephemeral ports. This should prevent
failures due to port conflicts in CI.
The change replaces the Vagrant box based fixture with a fixture
based on docker compose and 2 docker images, one for an openldap
server and one for a Shibboleth SAML Identity Provider.
The configuration of both openldap and shibboleth is identical to
the previous one, in order to minimize required changes in the
tests