Add leader_cluster_address field to sys/leader endpoint

The Vault API returns a `leader_cluster_address` field from the
/sys/leader endpoint, which provides the cluster address where the
leader is running (distinct from `leader_address` which is the API
address).

This change exposes that field through the `LeaderStatus` response
object as `cluster_address`.

Changes:
- Added `leader_cluster_address` field to `LeaderStatus` class
- Added test coverage for the new field
- Updated example documentation
- Updated CHANGELOG

Fixes #204

Author: chrisarcand

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## v?.??.? (Unreleased)
 
+IMPROVEMENTS
+
+- Added `cluster_address` field to `LeaderStatus` response from `sys/leader` endpoint [GH-204]
+
 BUG FIXES
 
 - Fixed `encode_path` incorrectly encoding hyphens (`-`), which caused 403 errors on Vault 1.15+ [GH-350, GH-343]

lib/vault/api/sys/leader.rb

@@ -18,6 +18,11 @@ class LeaderStatus < Response
     #   @return [String]
     field :leader_address, as: :address
 
+    # @!attribute [r] cluster_address
+    #   URL where the cluster leader is running.
+    #   @return [String]
+    field :leader_cluster_address, as: :cluster_address
+
     # @deprecated Use {#ha_enabled?} instead
     def ha?; ha_enabled?; end
 
@@ -35,7 +40,7 @@ class Sys
     # Determine the leader status for this vault.
     #
     # @example
-    #   Vault.sys.leader #=> #<Vault::LeaderStatus ha_enabled=false, is_self=false, leader_address="">
+    #   Vault.sys.leader #=> #<Vault::LeaderStatus ha_enabled=false, is_self=false, leader_address="", leader_cluster_address="">
     #
     # @return [LeaderStatus]
     def leader

spec/integration/api/sys/leader_spec.rb

@@ -17,6 +17,7 @@ module Vault
         expect(result.is_leader?).to be(false)
         expect(result.leader?).to be(false)
         expect(result.address).to eq("")
+        expect(result.cluster_address).to eq("")
       end
     end