deploy to google app engine flex (GAE flex)

[maxheld83]

I think GAE flex in some ways suits us better; it seems more mature, better documented and "cleaner" than Azure Web Apps for containers.

However, the pricing structure is a big, big disadvantage for typical shiny loads as explained in subugoe/shinycaas#11.
As of now, GAE flex will open a new VM for every version of every service, which gets very expensive fast and also just wastes a lot of empty cycles.

By contrast, in Azure Web Apps for Containers, we can run several apps and even their slots (~versions) in the same VM, which suits our loads much better.

Weirdly, this is actually kind of an inconsistent design in Azure, because a (micro)services architecture would imply that each of the services can be scaled independently, and sharing a VM kind of defeats that purpose.
But good for us, for now.

In the long run, a cleaner design such as GAE flex might be preferable, if:

• GAE flex allows <1 vCPU/Instance (RAM would still make it expensive)
• GAE flex allows us to share VMs (making it like Azure Web apps)
• GAE flex scales to 0 and/or Google Cloud Run allows websockets and/or miraculously allows stateful apps (not happening) subugoe/shinycaas#13

Anyway, keeping this open, might check back in a year or so.

Related: subugoe/hoad#25