add annotate

Signed-off-by: Jay Shao <shaoshijie830413@foxmail.com>
add some validation to user model

Signed-off-by: Jay Shao <shaoshijie830413@foxmail.com>
finish the user model

Signed-off-by: Jay Shao <shaoshijie830413@foxmail.com>
reannotate user model

Signed-off-by: Jay Shao <shaoshijie830413@foxmail.com>
Merge pull request #1 from jayshao830413/jay/modeling-users

Jay/modeling users