Organize ident in models code

making ident to soft tab, which is two spaces, to comply with ruby
coding style

Signed-off-by: walteryang <walteryang47@users.noreply.github.com>
Ensure role <-> operation relation unique in role_operation model

It validates unique combo of role_id colum and operation_id colum
in role_operations table

Signed-off-by: walteryang <walteryang47@users.noreply.github.com>