Currently, there's support for the Imagor image proxy. However, not everyone might be able to run or install it everywhere.

This PR adds a local image proxy which can be configured using the cdn_imagorServerUrl config. Currently, it has to be configured as <Base instance URL>/imageproxy.

1. Hash is supported so external users cannot use the proxy with different URLs
2. URL format is compatible with Imagor/Thumbor
3. Resizing is supported using the following fallbacks:
   1. Try sharp (requires C binaries for build)
   2. Try jimp (pure JS, added as optional dependency)
   3. Nothing, image is returned as-is

Discussion

(Doesn't have to be on GitHub, Spacebar/Discord is also possible.)

Code

• Can those @ts-expect-errors be fixed in a better way?
• Re: ^, currently, if jimp is installed, L153 is fine with the @ts-expect-error comment. If it isn't, TS complains about the directive being unused. How can this be fixed?

Concept

• I've currently limited the maximum Content-Length value to 10 MiB to prevent big files from overloading the server. Does this make sense? Is it better to, instead of waiting for the connection to finish, check the headers once they're received and instantly cancel the connection? Or does this not matter at all, and the limit should be removed completely?
• In which cases would the proxy be enabled after all? Should it be enabled only if cdn_imagorServerUrl includes /imageproxy?

Config

• Which kind of configs would be required for this? Suggestions:
  • Maximum file proxy size
  • Proxy timeout (currently set to 5 seconds)
  • Cache-Control header client cache duration