AI-1237 PG Backrest Restore

[dbarkowsky]

Summary

AI-1237

Changes

• md file with steps on completing restore process
• workflow file that hopefully makes things a bit easier

Testing

I've tested the steps manually, but I believe I have to test the workflows after merge.
Restore from an incremental backup was successful manually.

Checklist

By submitting this pull request, I acknowledge that I have attempted to meet the following:

• a self-review of my code
• commented code particularly in hard-to-understand areas
• corresponding changes to the documentation where required
• changes tested to the best of my ability
• no new errors or non-functional code