Add the possibility to duplicate a task to another project

app/Schema/Mysql.php

@@ -57,7 +57,7 @@ function version_18($pdo)
             status INT DEFAULT 0,
             time_estimated INT DEFAULT 0,
             time_spent INT DEFAULT 0,
-            task_id INT,
+            task_id INT NOT NULL,
             user_id INT,
             PRIMARY KEY (id),
             FOREIGN KEY(task_id) REFERENCES tasks(id) ON DELETE CASCADE

app/Schema/Postgres.php

@@ -143,7 +143,7 @@ function version_1($pdo)
             status SMALLINT DEFAULT 0,
             time_estimated INTEGER DEFAULT 0,
             time_spent INTEGER DEFAULT 0,
-            task_id INTEGER,
+            task_id INTEGER NOT NULL,
             user_id INTEGER,
             FOREIGN KEY(task_id) REFERENCES tasks(id) ON DELETE CASCADE
         );

app/Schema/Sqlite.php

@@ -57,7 +57,7 @@ function version_18($pdo)
             status INTEGER DEFAULT 0,
             time_estimated INTEGER DEFAULT 0,
             time_spent INTEGER DEFAULT 0,
-            task_id INTEGER,
+            task_id INTEGER NOT NULL,
             user_id INTEGER,
             FOREIGN KEY(task_id) REFERENCES tasks(id) ON DELETE CASCADE
         )"