refactor(relay): move replay metadata onto request bodies

relay/channel/task/sora/adaptor.go

@@ -216,9 +216,7 @@ func (a *TaskAdaptor) BuildRequestBody(c *gin.Context, info *relaycommon.RelayIn
 		return &buf, nil
 	}
 
-	info.UpstreamRequestBodySize = storage.Size()
-	info.UpstreamRequestGetBody = storage.NewReader
-	return common.ReaderOnly(storage), nil
+	return common.NewReplayableBodyReader(storage), nil
 }
 
 // DoRequest delegates to common helper.

relay/channel/task/sora/adaptor_test.go

@@ -14,7 +14,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestSoraBuildRequestBodyBindsReplayMetadataForPassThrough(t *testing.T) {
+func TestSoraBuildRequestBodyReturnsReplayablePassThroughBody(t *testing.T) {
 	payload := []byte("opaque-sora-request-body")
 	c, _ := gin.CreateTestContext(httptest.NewRecorder())
 	c.Request = httptest.NewRequest(http.MethodPost, "/v1/videos", bytes.NewReader(payload))
@@ -24,14 +24,15 @@ func TestSoraBuildRequestBodyBindsReplayMetadataForPassThrough(t *testing.T) {
 	info := &relaycommon.RelayInfo{}
 	body, err := (&TaskAdaptor{}).BuildRequestBody(c, info)
 	require.NoError(t, err)
+	replayable, ok := body.(common.ReplayableBody)
+	require.True(t, ok)
 
 	sent, err := io.ReadAll(body)
 	require.NoError(t, err)
 	assert.Equal(t, payload, sent)
-	assert.EqualValues(t, len(payload), info.UpstreamRequestBodySize)
-	require.NotNil(t, info.UpstreamRequestGetBody)
+	assert.EqualValues(t, len(payload), replayable.Size())
 
-	replayBody, err := info.UpstreamRequestGetBody()
+	replayBody, err := replayable.NewReader()
 	require.NoError(t, err)
 	replay, err := io.ReadAll(replayBody)
 	require.NoError(t, err)