MM-9556 Added ability to upload files without a multipart request (#8306)

* MM-9556 Added ability to upload files without a multipart request

* MM-9556 Handled some unusual test behaviour

api/file.go

@@ -76,7 +76,7 @@ func uploadFile(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	resStruct, err := c.App.UploadFiles(c.TeamId, channelId, c.Session.UserId, m.File["files"], m.Value["client_ids"])
+	resStruct, err := c.App.UploadMultipartFiles(c.TeamId, channelId, c.Session.UserId, m.File["files"], m.Value["client_ids"])
 	if err != nil {
 		c.Err = err
 		return