Add application setting to enable MinIO in offline transfer
In order to connect to a MinIO storage bucket, `fog` requires an `endpoint` url because fog uses `fog-aws` for both AWS object storage locations and MinIO instances. When and `endpoint` isn't provided, fog attempts to connect to an AWS S3 server by default. However, allowing any user to provide any URL to connect to an object storage location poses security risks, particularly on .com.
To mitigate these risks, an application setting that's disabled by default should be created to allow users who have a trusted MinIO instance to use it for offline transfer.
Related to https://gitlab.com/gitlab-org/gitlab/-/merge_requests/186032#note_2455157126 (confidential comment)
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