Use GitLab for Settings Sync

Problem to solve

Cannot use gitlab to sync vscode settings.

Current default options are github and microsoft
Can also use gitpod if you enable the option.
It would be nice to be able to use gitlab.

Proposal

Wait for upstream to implement support for custom settings sync backend Settings Sync : Allow for custom backend service end points, then implement that backend

Further details

Links / references

user manual
gitpod sync
Was not able to quickly locate api documentation for authentication/sync... will add if I find it.