Introduces:
- SAML Realm
- REST & Transport actions to support SAML single signon / signout
- Tests for above
- More XML than you ever wanted to see.
Original commit: elastic/x-pack-elasticsearch@b0fe7bb652
This creates a basic skeleton for the plugin split by adding folders and example
`build.gradle` files. It also includes a non-implemented `migrate-plugins.sh`
script that we can fill in at a later time.
Relates to elastic/x-pack-elasticsearch#2925
Original commit: elastic/x-pack-elasticsearch@2ab035d6b6