Define user.Email as sql.NullString to avoid unique constraint when email is empty in LDAP/OIDC
Separate the common/models/User with the pkg/user/dao/User
Fixes#10400
Signed-off-by: stonezdj <stonezdj@gmail.com>
This commit moves the legacy apis related to users to new model.
Some funcs under common/dao are left b/c they are used by other module,
which should also be shifted to leverage managers.
We'll handle them separately.
Signed-off-by: Daniel Jiang <jiangd@vmware.com>
