Updates should lock around the location they are updating

[Mr0grog]

When receiving data a high-frequency, we are sometimes running into issues where two parallel calls update the same location and both either try to create the same new update record or the same new location. We should probably use PG advisory locks on the ID or external IDs to prevent those calls from colliding.

[Mr0grog]

We probably need to do #463 before or as part of this.

[Mr0grog]

Additional cleanup since issue was originally written has largely mitigated the issue, but it would still be good to do this correctly as suggested here.

[Mr0grog]

This project has been shut down. This issue has been left open as a guide for anyone forking this project — addressing this issue (or at least knowing about it!) is likely to be worthwhile for you if you are maintaining a running copy or fork of UNIVAF.