fix: update keyedById to prevent infinite loops

This modifies the service plugin’s `addItems` mutation to prevent overwriting all of `keyedById` and `tempsById`.  When queries are made using data derived from the store, since the `addItems` mutation was overwriting the entire `keyedById` object, the query would run again.  These infinite loops were running even if you used a computed property as a go-between to cache the parts of the query derived from the store.

In scenarios where the query uses data derived from the store and then updates the store when results arrive, this change allows using a computed property to properly cache and prevent infinite loops.

Author: marshallswain

src/service-module/service-module.mutations.ts

@@ -23,9 +23,6 @@ export default function makeServiceMutations() {
     const Model = _get(models, `[${serverAlias}][${modelName}]`)
     const BaseModel = _get(models, `[${state.serverAlias}].BaseModel`)
 
-    const newKeyedById = { ...state.keyedById }
-    const newTempsById = { ...state.tempsById }
-
     for (let item of items) {
       const id = getId(item, idField)
       const isTemp = id === null || id === undefined
@@ -45,18 +42,15 @@ export default function makeServiceMutations() {
           tempId = assignTempId(state, item)
         }
         item.__isTemp = true
-        newTempsById[tempId] = item
+        Vue.set(state.tempsById, tempId, item)
       } else {
         // Only add the id if it's not already in the `ids` list.
         if (!state.ids.includes(id)) {
           state.ids.push(id)
         }
-        newKeyedById[id] = item
+        Vue.set(state.keyedById, id, item)
       }
     }
-
-    state.keyedById = newKeyedById
-    state.tempsById = newTempsById
   }
 
   function updateItems(state, items) {