[oniro] Mirror repositories doesn't work

Summary

I created several projects with mirror option, located at https://gitlab.eclipse.org/eclipse/oniro-core/third-party but they don't seem to be updating and aren't visible in Settings->Repository-Mirroring repositories, so I cannot force update nor change settings for the mirrors.

I tested the functionality in gitlab.com and it looks like they need to be added additionally in settings. Unfortunately I'm unable to do it. According to gitlab.com docs I should be Maintainer, and I am, but the setting seem to be restricted to admin.

Related to #1532 (comment 913911)

Steps to reproduce

Create new project as import project and "Repository by URL". Then add https://git.seco.com/pub/i.mx/yocto/5.x/meta-seco-imx.git as git repository URL and tick "Mirror repository". After successful project creation go to Settings->Repository-Mirroring repositories There will be empty "Mirrored repositories" list. Just add again https://git.seco.com/pub/i.mx/yocto/5.x/meta-seco-imx.git

What is the current bug behavior?

Unable to add the same repo in Settings->Repository-Mirroring repositories after creation of the project.

What is the expected correct behavior?

I should be able to add the same repository again via Settings->Repository-Mirroring repositories

Relevant logs and/or screenshots