Add configurable static asset hosting

[bennettgoble]

Allow static assets to be hosted directly by nginx using volume mounts and a list of desired bind locations defined using a STATIC_LOCATIONS environment variable.

Docker compose example:

services:
  app:
    # ...
    volumes:
      static:/var/www/static
  proxy:
    # ...
    environment:
      STATIC_LOCATIONS:/static/:/var/www/static/
    volumes:
      static:/var/www/static
volumes:
  static:

When deployed in ECS, the volumesFrom directive can be used.

Notes

• Switched from mo to gomplate for better enumeration and string manipulation
• Updated actions to newest standards

[jjlinden]

v cool

[bennettgoble]

I'm installing gomplate as a layer, but we could alternatively provide an OCI image for multiple platforms that applications could source from.