Global minimum sync time for mirrors

@tiagonbotelho is/was working on a feature that lets you set custom sync times for mirrors, on a per project basis. For GitLab.com we want to enforce a sensible minimum for all projects. For example, we want to set the minimum to either 12 or 24 hours. As a result, when determining the sync time the code has to check this minimum value. If the project's sync time is lower it will use the minimum instead.

cc @DouweM @tiagonbotelho @brodock

added ~978335 ~481018 labels

@tiagonbotelho Can we get this into 8.17?

assigned to @tiagonbotelho

changed milestone to %9.0

Currently we manually patched GitLab to set the sync time to 24 hours. This was necessary due to mirroring putting a lot of stress on the DB (see https://gitlab.com/gitlab-org/gitlab-ee/issues/1695).

Fixed by https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1217

closed