Fix warning on ActiveSupport::Cache.format_version

`Rail.application` was always evaluating to `nil` before as the code wasn't
running in an initializer.

Also make sure that `cache_format_version` is only rewritten in test environment
and ONLY if it'd raise a warning otherwise (and shift it back to the previous
value after the cache store is initialized). This should prevent the warning
while also having minimal impact out of the test environment.

Author: Drowze

lib/graphql/fragment_cache/railtie.rb

@@ -10,11 +10,6 @@ class Railtie < ::Rails::Railtie # :nodoc:
       module Config
         class << self
           def store=(store)
-            if Rails.version.to_f >= 7.0 && Rails.application
-              cache_format_version = 7.0
-              ActiveSupport::Cache.format_version = cache_format_version if cache_format_version
-            end
-
             # Handle both:
             #   store = :memory
             #   store = :mem_cache, ENV['MEMCACHE']
@@ -30,7 +25,14 @@ def store=(store)
       config.graphql_fragment_cache = Config
 
       if ENV["RACK_ENV"] == "test" || ENV["RAILS_ENV"] == "test"
-        config.graphql_fragment_cache.store = :null_store
+        initializer 'graphql-fragment_cache' do
+          if Rails.version.to_f >= 7.0 && ::ActiveSupport::Cache.format_version < 7.0
+            cache_format_version = ::ActiveSupport::Cache.format_version
+            ::ActiveSupport::Cache.format_version = 7.0
+            config.graphql_fragment_cache.store = :null_store
+            ::ActiveSupport::Cache.format_version = cache_format_version
+          end
+        end
       end
     end
   end