migrate gitLab repos via deploy token instead of personal token

[EngelPika32]

Feature Description

As the title says.
As of now, you can only migrate gitLab repos via a personal access token.
However, I propose this should be possible via a deploy token as well.

Additionally, using deploy tokens seems more secure, as you don't have to give access to all repos of an acc to a gitea instance but rather limit the access to the bare minimum required.

Screenshots

No response

[EngelPika32]

I've just noticed the issue described in #17763 – which possibly prevents the use of deploy tokens. The needed scope requires some clarification.

I still hope, deploy tokens become an option in the future.

Additionally, I'd like to add the following:

You only need one personal token per account, yet you enter one per migration. Personal tokens aren't scoped to a single repo.
They should be re-usable for multiple migrations. For that, they need to be added to your account settings instead.

I know, that you (a user) could save them somewhere else in order to enter the same token in multiple migrations, yet I don't think this should be the way to go.