Rename cost breakdown to breakdownByGlobalCluster

This is done to distinguish between breakdowns
by global cluster and by service modality

src/db/models/json/attachment.ts

@@ -13,16 +13,11 @@ const COST_ATTACHMENT_VALUE = t.intersection([
   t.exact(
     t.partial({
       /**
-       * When necessary, a cost breakdown can be provided with respect to a
-       * particular collection of objects.
-       *
-       * For example, when the object of this attachment is a governing entity,
-       * a breakdown needs to be provided for each of the global clusters,
-       * (even if the governing entity has 0 global clusters)
-       * and the total sum of the breakdown must match the overall cost when
-       * non-empty.
+       * When necessary, a cost breakdown can be provided for each of the global
+       * clusters (even if the governing entity has 0 global clusters), and the
+       * total sum of the breakdown must match the overall cost when non-empty.
        */
-      breakdown: t.array(
+      breakdownByGlobalCluster: t.array(
         t.exact(
           t.type({
             objectId: t.number,