[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/github.com/dsoprea/go-utility/v2/filesystem/graceful_copy.go

@@ -1,54 +0,0 @@
-package rifs
-
-import (
-	"fmt"
-	"io"
-)
-
-const (
-	defaultCopyBufferSize = 1024 * 1024
-)
-
-// GracefulCopy willcopy while enduring lesser normal issues.
-//
-// - We'll ignore EOF if the read byte-count is more than zero. Only an EOF when
-//   zero bytes were read will terminate the loop.
-//
-// - Ignore short-writes. If less bytes were written than the bytes that were
-//   given, we'll keep trying until done.
-func GracefulCopy(w io.Writer, r io.Reader, buffer []byte) (copyCount int, err error) {
-	if buffer == nil {
-		buffer = make([]byte, defaultCopyBufferSize)
-	}
-
-	for {
-		readCount, err := r.Read(buffer)
-		if err != nil {
-			if err != io.EOF {
-				err = fmt.Errorf("read error: %s", err.Error())
-				return 0, err
-			}
-
-			// Only break on EOF if no bytes were actually read.
-			if readCount == 0 {
-				break
-			}
-		}
-
-		writeBuffer := buffer[:readCount]
-
-		for len(writeBuffer) > 0 {
-			writtenCount, err := w.Write(writeBuffer)
-			if err != nil {
-				err = fmt.Errorf("write error: %s", err.Error())
-				return 0, err
-			}
-
-			writeBuffer = writeBuffer[writtenCount:]
-		}
-
-		copyCount += readCount
-	}
-
-	return copyCount, nil
-}