Save HostResources after host is saved

A Hosts's HostResources are determined during the validation step but not saved,
because the Host must exist before its HostResources can be stored (not-null database constraint).
We add a routine which saves the HostResources immediately after a Host is saved in case its Host.host_resources changed

app/models/concerns/foreman_resource_quota/host_managed_extensions.rb

@@ -19,6 +19,7 @@ module HostManagedExtensions
 
       # A host shall always have a .host_resources attribute
       before_validation :build_host_resources, unless: -> { host_resources.present? }
+      after_save :save_host_resources, if: -> { host_resources.changed? }
     end
 
     def verify_resource_quota
@@ -141,6 +142,10 @@ def quota_assigment_optional?
       owner.resource_quota_is_optional || Setting[:resource_quota_optional_assignment]
     end
 
+    def save_host_resources
+      host_resources.save
+    end
+
     # Wrap into a function for easier testing
     def call_utilization_helper(resources, hosts)
       all_host_resources, missing_hosts = utilization_from_resource_origins(resources, hosts)