Support using the custom video serving endpoint even if you don't use object storage (#2924)

* feat(video): refactor video serving endpoint

It can now be used without an object storage provider. Closes #2785

* fix: remove debug log

core/storageproviders/rewriteLocalPlaylist.go

@@ -0,0 +1,36 @@
+package storageproviders
+
+import (
+	"bufio"
+	"os"
+	"path/filepath"
+
+	"github.com/grafov/m3u8"
+	"github.com/owncast/owncast/config"
+	"github.com/owncast/owncast/core/playlist"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// rewriteRemotePlaylist will take a local playlist and rewrite it to have absolute URLs to remote locations.
+func rewriteRemotePlaylist(localFilePath, remoteServingEndpoint string) error {
+	f, err := os.Open(localFilePath) // nolint
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	p := m3u8.NewMasterPlaylist()
+	if err := p.DecodeFrom(bufio.NewReader(f), false); err != nil {
+		log.Warnln(err)
+	}
+
+	for _, item := range p.Variants {
+		item.URI = remoteServingEndpoint + filepath.Join("/hls", item.URI)
+	}
+
+	publicPath := filepath.Join(config.HLSStoragePath, filepath.Base(localFilePath))
+
+	newPlaylist := p.String()
+
+	return playlist.WritePlaylist(newPlaylist, publicPath)
+}