[EE] Port 10.3.4 security fixes into master

See merge request gitlab-org/gitlab-ee!4122

CE upstream - Tuesday

See merge request gitlab-org/gitlab-ee!4106

Docs: document new redirect for Disqus comments

See merge request gitlab-org/gitlab-ee!3976

Resolve "Failure in spec/migrations/fix_wrongly_renamed_routes_spec.rb"

Closes #4619 and #4622

See merge request gitlab-org/gitlab-ee!4119

Add some API endpoints for Geo admin screen in Vue

Closes #4475

See merge request gitlab-org/gitlab-ee!3923

Make Geo FDW configurable

Closes #4558

See merge request gitlab-org/gitlab-ee!4020

Signed-off-by: Rémy Coutable <remy@rymai.me>

Resolve "`promote-to-primary-node` silently fails reconfiguration due to postgresql service not listening"

Closes #4395

See merge request gitlab-org/gitlab-ee!4097

I hope this will fix the Geo failure.

Resolve "`promote-to-primary-node` silently fails reconfiguration due to postgresql service not listening"

`ObjectStorage::Concern` adds delegation to the model that
mount an uploader that uses `RecordsUploads::Concern` to track
its uploads. The basic implementation is to use the uploader
to build paths that can be used to fetch back the related `Upload`
instance so it can be used to build the uploader back (which is
needed to build the correct file URL).

I've demoted the ObjectStoreUploader to a concern that is mixed in
the concrete uploader classes that need to store files in a remote
object store.

I've been working on making the local -> remote migration working
first, which has been trivial compared to the remote -> local one.

The current implementation is heavily based on side-effects which
makes the code brittle and hard to reason about.

The current approach is to store the `store` field in the correct
`Upload` model once a migration has been done. To retrieve the field
I use the `has_many :uploads` relationship, with all the paths that
a certain file may have `uploads.where(path: paths).last`. This as
the drawback of adding a database query for every upload lookup, but
I feel that the generalization of this behavior is worth it. We should
be able to optimize this down the road quite easily.

Add missing CHANGELOG entry for 9.5.10 EE

See merge request gitlab-org/gitlab-ee!4115

Fix LDAP external user/group bug on first sign in

See merge request gitlab/gitlab-ee!569

[10.3] Check milestone access before persisting it on boards

See merge request gitlab/gitlab-ee!566

- `POST api/geo_nodes/:id/repair`: To repair the authentication
- `PUT api/geo_nodes/:id`: To edit the Geo node

Closes gitlab-org/gitlab-ee#4475.

[10.3] Prevent login with disabled OAuth providers

See merge request gitlab/gitlabhq!2296