Add support for custom mount paths in AppRole authentication

Adds optional mount parameter to approle() method to support AppRole
authentication against non-default mount points.

Usage:
  # Default mount point
  Vault.auth.approle(role_id, secret_id)

  # Custom mount point
  Vault.auth.approle(role_id, secret_id, mount: "my-approle")

The implementation uses an options hash (mount:) to maintain consistency
with other auth methods like userpass and ldap, and to allow for future
extensibility. Fully backward compatible - defaults to 'approle' mount.

Changes:
- Updated approle() to accept options hash with :mount parameter
- Fixed deprecated JSON.fast_generate to JSON.generate
- Added integration test for custom mount path
- Added documentation examples for both default and custom mounts
- Updated CHANGELOG

Co-authored-by: Laurent Lafage <laurent.lafage@fr.clara.net>

Author: chrisarcand

CHANGELOG.md

@@ -6,6 +6,7 @@ IMPROVEMENTS
 
 - Added `cluster_address` field to `LeaderStatus` response from `sys/leader` endpoint [GH-204]
 - Updated AppRole `set_role` documentation to include modern parameters like `secret_id_bound_cidrs`, `token_bound_cidrs`, and `token_policies`. Added reference to official Vault API docs for complete parameter list. [GH-220]
+- Added support for custom mount paths in AppRole authentication via `mount:` option [GH-292]
 
 BUG FIXES
 

lib/vault/api/auth.rb

@@ -81,21 +81,32 @@ def app_id(app_id, user_id, options = {})
     # successful, the resulting token will be stored on the client and used for
     # future requests.
     #
-    # @example
+    # @example Default mount point
     #   Vault.auth.approle(
     #     "db02de05-fa39-4855-059b-67221c5c2f63",
     #     "6a174c20-f6de-a53c-74d2-6018fcceff64",
     #   ) #=> #<Vault::Secret lease_id="">
     #
+    # @example Custom mount point
+    #   Vault.auth.approle(
+    #     "db02de05-fa39-4855-059b-67221c5c2f63",
+    #     "6a174c20-f6de-a53c-74d2-6018fcceff64",
+    #     mount: "my-approle"
+    #   ) #=> #<Vault::Secret lease_id="">
+    #
     # @param [String] role_id
     # @param [String] secret_id (default: nil)
     #   It is required when `bind_secret_id` is enabled for the specified role_id
+    # @param [Hash] options
+    # @option options [String] :mount (default: "approle")
+    #   The path where the approle auth backend is mounted
     #
     # @return [Secret]
-    def approle(role_id, secret_id=nil)
+    def approle(role_id, secret_id=nil, options = {})
+      mount = options[:mount] || 'approle'
       payload = { role_id: role_id }
       payload[:secret_id] = secret_id if secret_id
-      json = client.post("/v1/auth/approle/login", JSON.generate(payload))
+      json = client.post("/v1/auth/#{CGI.escape(mount)}/login", JSON.generate(payload))
       secret = Secret.decode(json)
       client.token = secret.auth.client_token
       return secret

spec/integration/api/auth_spec.rb

@@ -86,6 +86,33 @@ module Vault
           expect(subject.token).to eq(result.auth.client_token)
         end
       end
+
+      context "when using a custom mount path" do
+        before(:context) do
+          @custom_path = "custom-approle"
+          @custom_approle = "custom-role"
+          vault_test_client.sys.enable_auth(@custom_path, "approle", nil)
+
+          # Use logical.write to configure the role on the custom mount
+          vault_test_client.logical.write("auth/#{@custom_path}/role/#{@custom_approle}", {
+            secret_id_ttl: "10m",
+            token_ttl: "20m",
+          })
+
+          @role_id = vault_test_client.logical.read("auth/#{@custom_path}/role/#{@custom_approle}/role-id").data[:role_id]
+          @secret_id = vault_test_client.logical.write("auth/#{@custom_path}/role/#{@custom_approle}/secret-id", {}).data[:secret_id]
+        end
+
+        after(:context) do
+          vault_test_client.logical.delete("auth/#{@custom_path}/role/#{@custom_approle}")
+          vault_test_client.sys.disable_auth(@custom_path)
+        end
+
+        it "authenticates using the custom mount path" do
+          result = subject.auth.approle(@role_id, @secret_id, mount: @custom_path)
+          expect(subject.token).to eq(result.auth.client_token)
+        end
+      end
     end
 
     describe "#userpass" do