This change merges the "feature-internal-idp" branch into Elasticsearch.
This introduces a small identity-provider plugin as a child of the x-pack module.
This allows ES to act as a SAML IdP, for users who are authenticated against the
Elasticsearch cluster.
This feature is intended for internal use within Elastic Cloud environments
and is not supported for any other use case. It falls under an enterprise license tier.
The IdP is disabled by default.
Co-authored-by: Ioannis Kakavas <ioannis@elastic.co>
Co-authored-by: Tim Vernum <tim.vernum@elastic.co>
