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/both_versions.json

@@ -0,0 +1,12 @@
+{
+    "links": [
+        {
+            "rel": "http://nodeinfo.diaspora.software/ns/schema/2.0",
+            "href": "https://mobilizon.fr/.well-known/nodeinfo/2.0"
+        },
+        {
+            "rel": "http://nodeinfo.diaspora.software/ns/schema/2.1",
+            "href": "https://mobilizon.fr/.well-known/nodeinfo/2.1"
+        }
+    ]
+}