This commit overhauls the documentation of discovery and cluster coordination,
removing mention of the Zen Discovery module and replacing it with docs for the
new cluster coordination mechanism introduced in 7.0.
Relates #32006
This moves all Realm settings to an Affix definition.
However, because different realm types define different settings
(potentially conflicting settings) this requires that the realm type
become part of the setting key.
Thus, we now need to define realm settings as:
xpack.security.authc.realms:
file.file1:
order: 0
native.native1:
order: 1
- This is a breaking change to realm config
- This is also a breaking change to custom security realms (SecurityExtension)
