Add logstream interface and allow cloudwatchlogs to implement it (#294)

service/batchlogs/batchlogs.go

@@ -0,0 +1,13 @@
+package batchlogs
+
+import (
+	"context"
+	"io"
+)
+
+// batchlogs.Service contains functions for streaming logs in real time from a batch job
+type Service interface {
+	// Stream takes a batch job's log stream name and returns an io.ReadCloser
+	// containing the bytes of the log updated in real time
+	Stream(ctx context.Context, logName string) io.ReadCloser
+}