add started_at to sis_batches

refs CNVS-17788

so you can easily tell the difference between how long a batch took
vs. how long it took to start

test plan:
 * upload an SIS batch and let it run
 * when you view it via the API, it should include a started_at
   timestamp

Change-Id: I142024f82260c2ba690a950a09365e90c18cd43d
Reviewed-on: https://gerrit.instructure.com/47412
Reviewed-by: Rob Orton <rob@instructure.com>
Tested-by: Jenkins
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

app/models/sis_batch.rb

@@ -127,6 +127,7 @@ class SisBatch < ActiveRecord::Base
     if self.workflow_state == 'created'
       self.workflow_state = :importing
       self.progress = 0
+      self.started_at = Time.now.utc
       self.save
 
       import_scheme = SisBatch.valid_import_types[self.data[:import_type]]
@@ -201,7 +202,7 @@ class SisBatch < ActiveRecord::Base
       self.workflow_state = :failed
       self.workflow_state = :failed_with_messages if messages?
     end
-    self.ended_at = Time.now
+    self.ended_at = Time.now.utc
     self.save
   end
 
@@ -250,6 +251,7 @@ class SisBatch < ActiveRecord::Base
     self.options ||= {} # set this to empty hash if it does not exist so options[:stuff] doesn't blow up
     data = {
       "created_at" => self.created_at,
+      "started_at" => self.started_at,
       "ended_at" => self.ended_at,
       "updated_at" => self.updated_at,
       "progress" => self.progress,

db/migrate/20150119204052_add_started_at_to_sis_batches.rb

@@ -0,0 +1,7 @@
+class AddStartedAtToSisBatches < ActiveRecord::Migration
+  tag :predeploy
+
+  def change
+    add_column :sis_batches, :started_at, :datetime
+  end
+end

spec/apis/v1/sis_imports_api_spec.rb

@@ -52,6 +52,8 @@ describe SisImportsApiController, type: :request do
     json.delete("updated_at")
     expect(json.has_key?("ended_at")).to be_truthy
     json.delete("ended_at")
+    expect(json.has_key?("started_at")).to eq true
+    json.delete("started_at")
     if opts[:batch_mode_term_id]
       expect(json["batch_mode_term_id"]).not_to be_nil
     end
@@ -87,6 +89,8 @@ describe SisImportsApiController, type: :request do
     json.delete("updated_at")
     expect(json.has_key?("ended_at")).to be_truthy
     json.delete("ended_at")
+    expect(json.has_key?("started_at")).to eq true
+    json.delete("started_at")
     batch = SisBatch.last
     expect(json).to eq({
           "data" => { "import_type"=>"instructure_csv"},
@@ -115,6 +119,8 @@ describe SisImportsApiController, type: :request do
     json.delete("updated_at")
     expect(json.has_key?("ended_at")).to be_truthy
     json.delete("ended_at")
+    expect(json.has_key?("started_at")).to eq true
+    json.delete("started_at")
     expect(json).to eq({
           "data" => { "import_type" => "instructure_csv",
                       "supplied_batches" => ["user"],
@@ -499,6 +505,7 @@ describe SisImportsApiController, type: :request do
     json["sis_imports"].first.delete("created_at")
     json["sis_imports"].first.delete("updated_at")
     json["sis_imports"].first.delete("ended_at")
+    json["sis_imports"].first.delete("started_at")
 
     expect(json).to eq({"sis_imports"=>[{
                       "data" => { "import_type" => "instructure_csv",