Support alternate date formats in StateMachine.fromJson().

This commit fixes issue #2130.

Currently, `StateMachine.fromJson(...)` can parse JSON documents with timestamps in the format `2016-03-14T01:59:00.000Z` but it fails to parse JSON documents with timestamps in the format `2016-03-14T01:59:00Z`.

This is because we currently use `org.joda.time.format.ISODateTimeFormat.dateTime().parseDateTime(...)`, which requires fractional seconds in timestamps, for JSON date deserialization.

According to the documentation and examples in the AWS StepFunction documentation, fractional seconds in timestamps are optional.

This PR changes the date parsing logic to use `com.amazonaws.util.DateUtils.parseISO8601Date(...)` to parse dates during JSON deserialization. This method supports both the date format with fractional seconds and without fractional seconds.

This PR does not change the JSON serialization format of dates.

aws-java-sdk-stepfunctions/src/main/java/com/amazonaws/services/stepfunctions/builder/internal/DateModule.java

@@ -14,6 +14,7 @@
  */
 package com.amazonaws.services.stepfunctions.builder.internal;
 
+import com.amazonaws.util.DateUtils;
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.databind.DeserializationContext;
@@ -59,7 +60,7 @@ public Date deserialize(JsonParser jsonParser,
     }
 
     public static Date fromJson(String jsonText) {
-        return FORMATTER.parseDateTime(jsonText).toDate();
+        return DateUtils.parseISO8601Date(jsonText);
     }
 
 }

aws-java-sdk-stepfunctions/src/test/java/com/amazonaws/services/stepfunctions/builder/StepFunctionBuilderTest.java

@@ -667,4 +667,18 @@ public void stateMachineFromJson_MalformedJson_ThrowsException() {
         StateMachine.fromJson("{");
     }
 
+    @Test
+    public void stateMachineFromJson_JsonWithTimestampWithFractionalSeconds_DoesNotThrowException() {
+        StateMachine.fromJson(
+            "{\"StartAt\":\"TestTime\",\"States\":{\"TestTime\":{\"Type\":\"Wait\",\"Timestamp\":\"2016-03-14T01:59:00.000Z\",\"End\":true}}}"
+        );
+    }
+
+    @Test
+    public void stateMachineFromJson_JsonWithTimestampWithoutFractionalSeconds_DoesNotThrowException() {
+        StateMachine.fromJson(
+            "{\"StartAt\":\"TestTime\",\"States\":{\"TestTime\":{\"Type\":\"Wait\",\"Timestamp\":\"2016-03-14T01:59:00Z\",\"End\":true}}}"
+        );
+    }
+
 }