[bugfix] Wrap media in read closer (#941)

* use readcloser for content.Content

* call media postdata function no matter what

* return a readcloser from data func

* tidy of logic of readertostore

* fix whoopsie

internal/api/model/content.go

@@ -30,7 +30,7 @@ type Content struct {
 	// ContentLength in bytes
 	ContentLength int64
 	// Actual content
-	Content io.Reader
+	Content io.ReadCloser
 	// Resource URL to forward to if the file can be fetched from the storage directly (e.g signed S3 URL)
 	URL *url.URL
 }