Improve db SSH authorizations setup process

Storing SSH authorizations in the database is a prerequisite for geo and improves performance for large GitLab instances. It is also being back ported to GitLab CE (https://gitlab.com/gitlab-org/gitlab-ee/issues/3953) in support of Cloud Native.

We should make this feature easier to setup.

Currently it involves creating files as root, setting permissions and updating sshd_config. Much of this could be simplified.

Proposal

• Include authorized_keys bash script
• Set the permissions and ownership of the file correctly

Instructions would then be simplified to:

• Adding two lines to sshd_config and restarting the SSH service

Links

https://docs.gitlab.com/ee/administration/operations/fast_ssh_key_lookup.html