[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

1 files changed, 0 insertions, 57 deletions

diff --git a/vendor/github.com/go-errors/errors/error_backward.go b/vendor/github.com/go-errors/errors/error_backward.go
deleted file mode 100644
index 80b0695e7..000000000
--- a/vendor/github.com/go-errors/errors/error_backward.go
+++ /dev/null
@@ -1,57 +0,0 @@
-// +build !go1.13
-
-package errors
-
-import (
-	"reflect"
-)
-
-type unwrapper interface {
-	Unwrap() error
-}
-
-// As assigns error or any wrapped error to the value target points
-// to. If there is no value of the target type of target As returns
-// false.
-func As(err error, target interface{}) bool {
-	targetType := reflect.TypeOf(target)
-
-	for {
-		errType := reflect.TypeOf(err)
-
-		if errType == nil {
-			return false
-		}
-
-		if reflect.PtrTo(errType) == targetType {
-			reflect.ValueOf(target).Elem().Set(reflect.ValueOf(err))
-			return true
-		}
-
-		wrapped, ok := err.(unwrapper)
-		if ok {
-			err = wrapped.Unwrap()
-		} else {
-			return false
-		}
-	}
-}
-
-// Is detects whether the error is equal to a given error. Errors
-// are considered equal by this function if they are the same object,
-// or if they both contain the same error inside an errors.Error.
-func Is(e error, original error) bool {
-	if e == original {
-		return true
-	}
-
-	if e, ok := e.(*Error); ok {
-		return Is(e.Err, original)
-	}
-
-	if original, ok := original.(*Error); ok {
-		return Is(e, original.Err)
-	}
-
-	return false
-}