DEV: Follow-up to the lock step for services

This patch adds two things:

1. An outcome matcher (`on_lock_not_acquired`), allowing to react when
   there was a problem with the lock.
2. Compatibility with the steps inspector, allowing to display properly
   the steps of a service containing locks.

lib/service/base.rb

@@ -265,10 +265,11 @@ module Service
     class LockStep < Step
       include StepsHelpers
 
-      attr_reader :steps
+      attr_reader :steps, :keys
 
       def initialize(*keys, &block)
         @keys = keys
+        @name = keys.join(":")
         @steps = []
         instance_exec(&block)
       end
@@ -290,10 +291,12 @@ module Service
         end
       end
 
+      private
+
       def lock_name
         [
           context.__service_class__.to_s.underscore,
-          *@keys.flat_map { |key| [key, context[:params].send(key)] },
+          *keys.flat_map { |key| [key, context[:params].public_send(key)] },
         ].join(":")
       end
     end

lib/service/runner.rb

@@ -25,6 +25,8 @@
 # * +on_exceptions(*exceptions)+: will execute the provided block if any
 #   exceptions were caught by the `try` block. One or more exception classes
 #   can be provided to specifically handle those exceptions.
+# * +on_lock_not_acquired(*keys)+: will execute the provided block if the lock
+#   using `keys` wasn’t acquired successfully.
 #
 # All the specialized steps receive the failing step result object as an
 # argument to their block. `on_model_errors` receives the actual model so it’s
@@ -105,6 +107,10 @@ class Service::Runner
       name: "default",
       property: :exception,
     },
+    on_lock_not_acquired: {
+      condition: ->(*keys) { failure_for?("result.lock.#{keys.join(":")}") },
+      key: [],
+    },
   }.with_indifferent_access.freeze
 
   # @!visibility private

lib/service/steps_inspector.rb

@@ -123,6 +123,17 @@ class Service::StepsInspector
     end
   end
 
+  # @!visibility private
+  class Lock < Transaction
+    def inspect
+      "#{"  " * nesting_level}[#{inspect_type}] #{name}#{runtime} #{emoji}".rstrip
+    end
+
+    def error
+      "Lock '#{name}' was not acquired."
+    end
+  end
+
   attr_reader :steps, :result
 
   def initialize(result)