implemented more /sample methods

src/test/db.json

@@ -61,7 +61,7 @@
         "_id": {"$oid":"500000000000000000000002"},
         "comment": "",
         "sample_references": [{
-          "id": "400000000000000000000004",
+          "id": {"$oid":"400000000000000000000004"},
           "relation": "granulate to sample"
         }],
         "custom_fields": {
@@ -73,11 +73,12 @@
         "_id": {"$oid":"500000000000000000000003"},
         "comment": "",
         "sample_references": [{
-          "id": "400000000000000000000003",
+          "id": {"$oid":"400000000000000000000003"},
           "relation": "part to sample"
         }],
         "custom_fields": {
-          "not allowed for new applications": true
+          "not allowed for new applications": true,
+          "another_field": "is there"
         },
         "__v": 0
       }
@@ -88,6 +89,12 @@
         "name": "not allowed for new applications",
         "qty": 2,
         "__v": 0
+      },
+      {
+        "_id": {"$oid":"600000000000000000000002"},
+        "name": "another_field",
+        "qty": 1,
+        "__v": 0
       }
     ],
     "materials": [