XL: Rename objectN to part.N (#2019)

Fixes #2015

docs/backend/xl/uploads.json

@@ -1,5 +1,5 @@
 {
-    "version": "1",
+    "version": "1.0.0",
     "format": "xl",
     "uploadIds": [
         {

docs/backend/xl/xl.json

@@ -4,19 +4,13 @@
             "number": 1,
             "size": 5242880,
             "etag": "3565c6e741e69a007a5ac7db893a62b5",
-            "name": "object1"
+            "name": "part.1"
         },
         {
             "number": 2,
             "size": 5242880,
             "etag": "d416712335c280ab1e39498552937764",
-            "name": "object2"
-        },
-        {
-            "number": 3,
-            "size": 4338324,
-            "etag": "8a98c5c54d81c6c95ed9bdcaeb941aaf",
-            "name": "object3"
+            "name": "part.2"
         }
     ],
     "meta": {
@@ -36,12 +30,12 @@
         "data": 5,
         "checksum": [
             {
-                "name": "object1",
+                "name": "part.1",
                 "algorithm": "blake2b",
                 "hash": "173c2cda7fb9e2798f91ba10135b65475fd2b97684355b328941d1c470a37549502672b2b4630c8268d5e5f79c8eb2fe433a25c6368f31d75b2c0504e3104c0e",
             },
             {
-                "name": "object2",
+                "name": "part.2",
                 "algorithm": "blake2b",
                 "hash": "14f9ba0006b2db7cd171507e79032ad3a34eab7df02b6564c487614b6d1e6613343a4f56074aa3473ac9c3b26e00cbbeae937d478cca4cfb138e72838ebb0826",
             },
@@ -53,5 +47,5 @@
         "size": 14824084
     },
     "format": "xl",
-    "version": "1"
+    "version": "1.0.0"
 }