feat(nodeinfo): extract and save NodeInfo information from instances to display it on instances list

We also try to detect the application actor if it's not given by NodeInfo metadata (FEP-2677)
(guessing for Mobilizon, PeerTube & Mastodon).

Closes #1392

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

test/fixtures/nodeinfo/data.json

@@ -0,0 +1,29 @@
+{
+    "version": "2.1",
+    "protocols": [
+        "activitypub"
+    ],
+    "metadata": {
+        "nodeDescription": "Mobilizon.fr est l'instance Mobilizon de Framasoft.",
+        "nodeName": "Mobilizon"
+    },
+    "usage": {
+        "users": {
+            "total": 9204
+        },
+        "localComments": 3253,
+        "localPosts": 7545
+    },
+    "services": {
+        "outbound": [
+            "atom1.0"
+        ],
+        "inbound": []
+    },
+    "software": {
+        "name": "Mobilizon",
+        "version": "4.0.2",
+        "repository": "https://framagit.org/framasoft/mobilizon"
+    },
+    "openRegistrations": true
+}