fix: Support creating ongoing Legal Hold policy with start date

Closes: SDK-4293

src/main/java/com/box/sdk/BoxLegalHoldPolicy.java

@@ -101,14 +101,33 @@ public static BoxLegalHoldPolicy.Info create(BoxAPIConnection api, String name,
      * @return information about the Legal Hold Policy created.
      */
     public static BoxLegalHoldPolicy.Info createOngoing(BoxAPIConnection api, String name, String description) {
+        return createOngoing(api, name, description, null);
+    }
+
+
+    /**
+     * Creates a new ongoing Legal Hold Policy.
+     *
+     * @param api         the API connection to be used by the resource.
+     * @param name        the name of Legal Hold Policy.
+     * @param description the description of Legal Hold Policy.
+     * @param filterStartedAt optional date filter applies to Custodian assignments only.
+     * @return information about the Legal Hold Policy created.
+     */
+    public static BoxLegalHoldPolicy.Info createOngoing(
+            BoxAPIConnection api, String name, String description, Date filterStartedAt
+    ) {
         URL url = ALL_LEGAL_HOLD_URL_TEMPLATE.build(api.getBaseURL());
         BoxJSONRequest request = new BoxJSONRequest(api, url, "POST");
         JsonObject requestJSON = new JsonObject()
-            .add("policy_name", name)
-            .add("is_ongoing", true);
+                .add("policy_name", name)
+                .add("is_ongoing", true);
         if (description != null) {
             requestJSON.add("description", description);
         }
+        if (filterStartedAt != null) {
+            requestJSON.add("filter_started_at", BoxDateFormat.format(filterStartedAt));
+        }
         request.setBody(requestJSON.toString());
         try (BoxJSONResponse response = request.send()) {
             JsonObject responseJSON = Json.parse(response.getJSON()).asObject();

src/test/Fixtures/BoxLegalHold/PostOngoingWithStartDateLegalHoldPolicies201.json

@@ -0,0 +1,25 @@
+{
+  "type": "legal_hold_policy",
+  "id": "11111",
+  "policy_name": "Trial Documents",
+  "description": "This is a description.",
+  "status": "active",
+  "assignment_counts": {
+    "user": 0,
+    "folder": 0,
+    "file": 0,
+    "file_version": 0
+  },
+  "is_ongoing": true,
+  "created_by": {
+    "type": "user",
+    "id": "33333",
+    "name": "Test User",
+    "login": "testuser@example.com"
+  },
+  "created_at": "2018-04-25T16:37:05-07:00",
+  "modified_at": "2018-04-25T16:37:05-07:00",
+  "deleted_at": null,
+  "filter_started_at": "2018-04-25T16:37:05-07:00",
+  "filter_ended_at": null
+}

src/test/java/com/box/sdk/BoxLegalHoldPolicyTest.java

@@ -189,6 +189,47 @@ public void testCreateOngoingNewLegalHoldPolicySucceedsAndSendsCorrectJson() {
         Assert.assertTrue(policyInfo.getIsOngoing());
     }
 
+    @Test
+    public void testCreateOngoingWithSTartDateNewLegalHoldPolicySucceedsAndSendsCorrectJson() throws ParseException {
+        final String legalHoldsURL = "/2.0/legal_hold_policies";
+        final String policyID = "11111";
+        final String createdByID = "33333";
+        final String createdByName = "Test User";
+        final String createdByLogin = "testuser@example.com";
+        final String policyName = "Trial Documents";
+        final String description = "This is a description.";
+        final String startTimeString = "2018-04-25T23:37:05Z";
+        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssX");
+        final Date startTime = dateFormat.parse("2018-04-25T16:37:05-07:00");
+
+        JsonObject policyObject = new JsonObject()
+                .add("policy_name", policyName)
+                .add("is_ongoing", true)
+                .add("description", description)
+                .add("filter_started_at", startTimeString);
+
+        String result = TestUtils.getFixture("BoxLegalHold/PostOngoingWithStartDateLegalHoldPolicies201");
+
+        wireMockRule.stubFor(WireMock.post(WireMock.urlPathEqualTo(legalHoldsURL))
+                .withRequestBody(WireMock.equalToJson(policyObject.toString()))
+                .willReturn(WireMock.aResponse()
+                        .withHeader("Content-Type", APPLICATION_JSON)
+                        .withBody(result)));
+
+        BoxLegalHoldPolicy.Info policyInfo = BoxLegalHoldPolicy.createOngoing(
+                this.api, policyName, description, startTime
+        );
+
+        Assert.assertEquals(policyID, policyInfo.getID());
+        Assert.assertEquals(createdByID, policyInfo.getCreatedBy().getID());
+        Assert.assertEquals(createdByName, policyInfo.getCreatedBy().getName());
+        Assert.assertEquals(createdByLogin, policyInfo.getCreatedBy().getLogin());
+        Assert.assertEquals(policyName, policyInfo.getPolicyName());
+        Assert.assertEquals(description, policyInfo.getDescription());
+        Assert.assertEquals(startTime, policyInfo.getFilterStartedAt());
+        Assert.assertTrue(policyInfo.getIsOngoing());
+    }
+
 
     @Test
     public void testUpdateLegalHoldPolicySucceedsAndSendsCorrectJson() {