due date picker matches anywhere in the string

fixes CNVS-21000

test plan:
  - go to new assignment page
  - search by a students last name
  - you are able to find the student this way

Change-Id: I909b72aa74e4245a56bc3a9839a5ebb075116f2e
Reviewed-on: https://gerrit.instructure.com/55912
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Jenkins
QA-Review: Adam Stone <astone@instructure.com>
Product-Review: Jason Sparks <jsparks@instructure.com>

Author: Michael Nomitch

app/jsx/due_dates/DueDateTokenWrapper.jsx

@@ -77,7 +77,7 @@ define([
 
     findMatchingOption(userInput){
       if(typeof userInput !== 'string') { return userInput }
-      return this.enumerableStartsWith(userInput, _.find)
+      return this.enumerableContainsString(userInput, _.find)
     },
 
     suppressKeys(e){
@@ -102,9 +102,9 @@ define([
       })
     },
 
-    enumerableStartsWith(userInput, enumerable){
+    enumerableContainsString(userInput, enumerable){
       var escapedInput = rEscape(userInput)
-      var filter = new RegExp('^' + escapedInput, 'i')
+      var filter = new RegExp(escapedInput, 'i')
       return enumerable(this.props.potentialOptions, function(option){
         return filter.test(option.name)
       })
@@ -116,7 +116,7 @@ define([
 
     filteredTags() {
       if (this.state.userInput === '') return this.props.potentialOptions
-      return this.enumerableStartsWith(this.state.userInput, _.filter)
+      return this.enumerableContainsString(this.state.userInput, _.filter)
     },
 
     // -------------------

spec/coffeescripts/jsx/due_dates/DueDateTokenWrapperSpec.coffee

@@ -21,7 +21,7 @@ define [
         ]
         potentialOptions: [
           {course_section_id: "1", name: "Patricians"},
-          {id: "1", name: "Seneca"},
+          {id: "1", name: "Seneca The Elder"},
           {id: "2", name: "Agrippa"},
           {id: "3", name: "Publius"},
           {id: "4", name: "Scipio"},
@@ -69,7 +69,7 @@ define [
     equal @DueDateTokenWrapper.optionsForMenu()[1].props.value, "course_section"
     equal @DueDateTokenWrapper.optionsForMenu()[2].props.value, "Patricians"
     equal @DueDateTokenWrapper.optionsForMenu()[4].props.value, "student"
-    equal @DueDateTokenWrapper.optionsForMenu()[5].props.value, "Seneca"
+    equal @DueDateTokenWrapper.optionsForMenu()[5].props.value, "Seneca The Elder"
 
   test 'handleTokenAdd is called when a token is added', ->
     addProp = @sandbox.stub(@DueDateTokenWrapper.props, "handleTokenAdd")
@@ -90,3 +90,7 @@ define [
   test 'findMatchingOption can handle strings with weird characters', ->
     foundToken = @DueDateTokenWrapper.findMatchingOption("Plebs | [")
     equal foundToken["name"], "Plebs | [ $"
+
+  test 'findMatchingOption can match characters in the middle of a string', ->
+    foundToken = @DueDateTokenWrapper.findMatchingOption("The Elder")
+    equal foundToken["name"], "Seneca The Elder"