[feature] support processing of (many) more media types (#3090)

* initial work replacing our media decoding / encoding pipeline with ffprobe + ffmpeg

* specify the video codec to use when generating static image from emoji

* update go-storage library (fixes incompatibility after updating go-iotools)

* maintain image aspect ratio when generating a thumbnail for it

* update readme to show go-ffmpreg

* fix a bunch of media tests, move filesize checking to callers of media manager for more flexibility

* remove extra debug from error message

* fix up incorrect function signatures

* update PutFile to just use regular file copy, as changes are file is on separate partition

* fix remaining tests, remove some unneeded tests now we're working with ffmpeg/ffprobe

* update more tests, add more code comments

* add utilities to generate processed emoji / media outputs

* fix remaining tests

* add test for opus media file, add license header to utility cmds

* limit the number of concurrently available ffmpeg / ffprobe instances

* reduce number of instances

* further reduce number of instances

* fix envparsing test with configuration variables

* update docs and configuration with new media-{local,remote}-max-size variables

vendor/codeberg.org/gruf/go-iotools/close.go

@@ -2,6 +2,13 @@ package iotools
 
 import "io"
 
+// NopCloser is an empty
+// implementation of io.Closer,
+// that simply does nothing!
+type NopCloser struct{}
+
+func (NopCloser) Close() error { return nil }
+
 // CloserFunc is a function signature which allows
 // a function to implement the io.Closer type.
 type CloserFunc func() error
@@ -10,6 +17,7 @@ func (c CloserFunc) Close() error {
 	return c()
 }
 
+// CloserCallback wraps io.Closer to add a callback deferred to call just after Close().
 func CloserCallback(c io.Closer, cb func()) io.Closer {
 	return CloserFunc(func() error {
 		defer cb()
@@ -17,6 +25,7 @@ func CloserCallback(c io.Closer, cb func()) io.Closer {
 	})
 }
 
+// CloserAfterCallback wraps io.Closer to add a callback called just before Close().
 func CloserAfterCallback(c io.Closer, cb func()) io.Closer {
 	return CloserFunc(func() (err error) {
 		defer func() { err = c.Close() }()