[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, 16 insertions, 14 deletions

diff --git a/internal/media/manager.go b/internal/media/manager.go
index ea126e460..aaf9448b8 100644
--- a/internal/media/manager.go
+++ b/internal/media/manager.go
@@ -314,21 +314,26 @@ func (m *Manager) RefreshEmoji(
 
 	// Since this is a refresh we will end up storing new images at new
 	// paths, so we should wrap closer to delete old paths at completion.
-	wrapped := func(ctx context.Context) (io.ReadCloser, int64, error) {
+	wrapped := func(ctx context.Context) (io.ReadCloser, error) {
 
-		// Call original data func.
-		rc, sz, err := data(ctx)
+		// Call original func.
+		rc, err := data(ctx)
 		if err != nil {
-			return nil, 0, err
+			return nil, err
 		}
 
-		// Wrap closer to cleanup old data.
-		c := iotools.CloserFunc(func() error {
+		// Cast as separated reader / closer types.
+		rct, ok := rc.(*iotools.ReadCloserType)
 
-			// First try close original.
-			if rc.Close(); err != nil {
-				return err
-			}
+		if !ok {
+			// Allocate new read closer type.
+			rct = new(iotools.ReadCloserType)
+			rct.Reader = rc
+			rct.Closer = rc
+		}
+
+		// Wrap underlying io.Closer type to cleanup old data.
+		rct.Closer = iotools.CloserCallback(rct.Closer, func() {
 
 			// Remove any *old* emoji image file path now stream is closed.
 			if err := m.state.Storage.Delete(ctx, oldPath); err != nil &&
@@ -341,12 +346,9 @@ func (m *Manager) RefreshEmoji(
 				!storage.IsNotFound(err) {
 				log.Errorf(ctx, "error deleting old static emoji %s from storage: %v", shortcodeDomain, err)
 			}
-
-			return nil
 		})
 
-		// Return newly wrapped readcloser and size.
-		return iotools.ReadCloser(rc, c), sz, nil
+		return rct, nil
 	}
 
 	// Use a new ID to create a new path