[OStatus] Port remote-follow to the RemoteFollow plugin

OStatusPlugin:
- Stop adding the remote-follow button
- Subscribe to required RemoteFollow plugin events
- Drop main/ostatussub route and update urls to the main/RemoteFollowSub route
- Bump plugin minor version number

actions/ostatusgroup,
actions/ostatuspeopletag:
- Update urls to the main/RemoteFollowSub route

lib/util:
- Port required functions from OStatusSubAction and adapt to be used with the new events

plugins/OStatus/lib/util.php

@@ -0,0 +1,64 @@
+<?php
+// This file is part of GNU social - https://www.gnu.org/software/social
+//
+// GNU social is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// GNU social is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with GNU social.  If not, see <http://www.gnu.org/licenses/>.
+
+defined('GNUSOCIAL') || die();
+
+/**
+ * Pull (and store) remote profile from the its uri
+ * 
+ * @param string $uri
+ * @return null|Ostatus_profile
+ */
+function pullRemoteProfile(string $uri): ?Ostatus_profile
+{
+    $validate = new Validate();
+
+    try {
+        $uri = Discovery::normalize($uri);
+    } catch (Exception $e) {
+        return null;
+    }
+
+    try {
+        if (Discovery::isAcct($uri) && $validate->email(mb_substr($uri, 5))) {
+            $profile = Ostatus_profile::ensureWebfinger($uri);
+        } else if ($validate->uri($uri)) {
+            $profile = Ostatus_profile::ensureProfileURL($uri);
+        } else {
+            common_log(LOG_ERR, 'Invalid address format.');
+            return null;
+        }
+        return $profile;
+    } catch (FeedSubBadURLException $e) {
+        common_log(LOG_ERR, 'Invalid URL or could not reach server.');
+    } catch (FeedSubBadResponseException $e) {
+        common_log(LOG_ERR, 'Cannot read feed; server returned error.');
+    } catch (FeedSubEmptyException $e) {
+        common_log(LOG_ERR, 'Cannot read feed; server returned an empty page.');
+    } catch (FeedSubBadHTMLException $e) {
+        common_log(LOG_ERR, 'Bad HTML, could not find feed link.');
+    } catch (FeedSubNoFeedException $e) {
+        common_log(LOG_ERR, 'Could not find a feed linked from this URL.');
+    } catch (FeedSubUnrecognizedTypeException $e) {
+        common_log(LOG_ERR, 'Not a recognized feed type.');
+    } catch (FeedSubNoHubException $e) {
+        common_log(LOG_ERR, 'No hub found.');
+    } catch (Exception $e) {
+        common_log(LOG_ERR, sprintf('Bad feed URL: %s %s', get_class($e), $e->getMessage()));
+    }
+
+    return null;
+}