* Add ETag caching support
* Update the readme file
* Typo
* Calculate ETag before image processing, rename Env Var
* Make PO struct field public
* Generate random value on server startup to be used in ETag calculation
* Minor refactoring
* Adjust boolean value parsing as discussed in GitHub PR page
* Move random value generation to the config
* Update README
* Revert changes
* Use footprint to calculate the hash of an image
Returns 200 OK after server starts.
This greatly simplifies container deployment. For example,
Kubernetes can be configured to not route traffic to imgproxy Pods
that did not pass Readiness check against /health.