Deprecate InvalidateElementsCacheJob

Alchemy Core now has the same feature. Since jobs
still might be enqueued in the background job processor,
we deprecate it instead if removing it, although this
extension will not enqueue new jobs.

Author: tvdeyen

app/jobs/alchemy/solidus/invalidate_elements_cache_job.rb

@@ -4,6 +4,11 @@ class InvalidateElementsCacheJob < BaseJob
       queue_as :default
 
       def perform(model_name, id)
+        Alchemy::Deprecation.warn <<~WARN
+          Alchemy::Solidus::InvalidateElementsCacheJob is deprecated and will be removed in 9.0.
+          Please use Alchemy::InvalidateElementsCacheJob instead.
+        WARN
+
         now = Time.current
 
         element_ids = model(model_name)