A part of https://github.com/go-gitea/gitea/pull/22865
At first, I think we do not need 3 ProjectTypes, as we can check user
type, but it seems that it is not database friendly.
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Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: 6543 <6543@obermui.de>
