Fix ISSUE schema.

- MILESTONE_ID is NULLABLE
- Add ASIGNED_USER_NAME column

src/main/resources/update/1_0.sql

@@ -31,7 +31,8 @@ CREATE TABLE ISSUE(
 		REPOSITORY_NAME VARCHAR(100) NOT NULL,
 		ISSUE_ID INT NOT NULL,
 		OPENED_USER_NAME VARCHAR(100) NOT NULL,
-		MILESTONE_ID INT NOT NULL,
+		MILESTONE_ID INT,
+		ASSIGNED_USER_NAME VARCHAR(100),
 		TITLE TEXT NOT NULL,
 		CONTENT TEXT NOT NULL,
 		REGISTERED_DATE TIMESTAMP NOT NULL,