fix(sent): Do not allow sent or drafts to be modified

- Specifically, when dragging from the sent perspective, we should not
  allow the sent label to be removed.
- If moved to trash or spam, `all mail` will be correctly removed from
  the thread, but it will keep sent label
- Show sent MailLabel on the threads

spec/models/category-spec.coffee

@@ -58,5 +58,5 @@ describe 'Category', ->
       cat.name = 'sent'
       expect(cat.isUserCategory()).toBe false
       expect(cat.isStandardCategory()).toBe true
-      expect(cat.isHiddenCategory()).toBe true
+      expect(cat.isHiddenCategory()).toBe false
       expect(cat.isLockedCategory()).toBe true

spec/models/thread-spec.coffee

@@ -70,8 +70,8 @@ describe 'Thread', ->
       expect(actualOut.length).toBe 1
       expect(actualOut[0].displayName).toBe 'not important'
 
-    it "doesn't display 'sent', 'all', 'archive', or 'drafts'", ->
-      inputs = ['sent', 'all', 'archive', 'drafts']
+    it "doesn't display 'all', 'archive', or 'drafts'", ->
+      inputs = ['all', 'archive', 'drafts']
       actualOut = sortedForCategoryNames inputs
       expect(actualOut.length).toBe 0
 

src/flux/models/category.coffee

@@ -18,11 +18,11 @@ StandardCategories = {
 
 LockedCategories = {
   "sent"
+  "drafts"
   "N1-Snoozed"
 }
 
 HiddenCategories = {
-  "sent"
   "drafts"
   "all"
   "archive"

src/mailbox-perspective.coffee

@@ -305,14 +305,17 @@ class CategoryMailboxPerspective extends MailboxPerspective
 
   receiveThreads: (threadsOrIds) =>
     FocusedPerspectiveStore = require './flux/stores/focused-perspective-store'
-    currentCategories = FocusedPerspectiveStore.current().categories()
+    current= FocusedPerspectiveStore.current()
 
     # This assumes that the we don't have more than one category per accountId
     # attached to this perspective
     DatabaseStore.modelify(Thread, threadsOrIds).then (threads) =>
       tasks = TaskFactory.tasksForApplyingCategories
         threads: threads
-        categoriesToRemove: (accountId) -> _.filter(currentCategories, _.matcher({accountId}))
+        categoriesToRemove: (accountId) ->
+          if current.categoriesSharedName() in Category.LockedCategoryNames
+            return []
+          return _.filter(current.categories(), _.matcher({accountId}))
         categoriesToAdd: (accountId) => [_.findWhere(@_categories, {accountId})]
       Actions.queueTasks(tasks)