Override `created_at` value with `planted_at` value when available

app/serializers/base_point_serializer.rb

@@ -1,6 +1,24 @@
 class BasePointSerializer < ApplicationSerializer
   attributes :device_id, :name, :pointer_type, :meta, :x, :y, :z
 
+  # PROBLEM:
+  #   * Users need a mutable way to mark a plant's creation time => `planted_at`
+  #   * DB Admin needs to know the _real_ created_at time.
+  #   * We can't change field names (or destroy data) that is in use by legacy devices
+  #
+  # SOLUTION:
+  #   * Don't allow users to modify `created_at`
+  #   * Provide `planted_at` if possible.
+  #   * Always provide `planted_at` if it is available
+  #   * Provide a read-only view of `created_at` if `planted_at` is `nil`
+  def planted_at
+    object.planted_at || object.created_at
+  end
+
+  def created_at
+    planted_at
+  end
+
   def meta
     object.meta || {}
   end

app/serializers/plant_serializer.rb

@@ -1,10 +1,6 @@
 class PlantSerializer < BasePointSerializer
   attributes :openfarm_slug, :plant_stage, :planted_at, :radius, :meta
 
-  def planted_at
-    object.planted_at || object.created_at
-  end
-
   def x
     object.x.round
   end