[deviantart] extend 'metadata' option (#5175)

alloe fetching extended metadata in addition to the usual
'description', 'tags', etc by setting 'metadata' to a list of
'camera', 'stats', 'submission', 'collection', and 'gallery'

for example "metadata": "stats,submission"

test/results/deviantart.py

@@ -642,6 +642,37 @@ __tests__ = (
     "#sha1_content": "6a7c74dc823ebbd457bdd9b3c2838a6ee728091e",
 },
 
+{
+    "#url"     : "https://www.deviantart.com/shimoda7/art/For-the-sake-10073852",
+    "#category": ("", "deviantart", "deviation"),
+    "#class"   : deviantart.DeviantartDeviationExtractor,
+    "#options" : {"metadata": "submission,camera,stats"},
+
+    "can_post_comment": False,
+    "description"     : str,
+    "is_watching"     : False,
+    "license"         : "No License",
+    "stats": {
+        "comments"       : int,
+        "downloads"      : int,
+        "downloads_today": int,
+        "favourites"     : int,
+        "views"          : int,
+        "views_today"    : int,
+    },
+    "submission": {
+        "category"      : "traditional/drawings/other",
+        "creation_time" : "2004-08-25T02:44:08-0700",
+        "file_size"     : "133 KB",
+        "resolution"    : "710x510",
+        "submitted_with": {
+            "app": "Unknown App",
+            "url": ""
+        },
+    },
+    "tags": [],
+},
+
 {
     "#url"     : "https://www.deviantart.com/zzz/art/zzz-1234567890",
     "#category": ("", "deviantart", "deviation"),