Fix some federation issues (#357)

* Fix some follow issues

Fix not receiving notifications when followed by remote users
Fix imposibility to be unfollowed by Mastodon/Pleroma users (tested only against Pleroma)

* Fix notification on every post

* Fix issues with federation

Send Link instead of Object when emiting Follow request
Receive both Link and Object for Follow request
Don't panic when fetching user with no followers or posts from Pleroma
Reorder follower routes so Activity Pub one is reachable

* Generate absolute urls for mentions and tags

* Verify author when undoing activity by Link

plume-models/src/posts.rs

@@ -431,8 +431,8 @@ impl Post {
     }
 
     pub fn to_activity(&self, conn: &Connection) -> LicensedArticle {
-        let mut to = self.get_receivers_urls(conn);
-        to.push(PUBLIC_VISIBILTY.to_string());
+        let cc = self.get_receivers_urls(conn);
+        let to  = vec![PUBLIC_VISIBILTY.to_string()];
 
         let mut mentions_json = Mention::list_for_post(conn, self.id)
             .into_iter()
@@ -526,7 +526,7 @@ impl Post {
             .expect("Post::to_activity: to error");
         article
             .object_props
-            .set_cc_link_vec::<Id>(vec![])
+            .set_cc_link_vec::<Id>(cc.into_iter().map(Id::new).collect())
             .expect("Post::to_activity: cc error");
         let mut license = Licensed::default();
         license.set_license_string(self.license.clone()).expect("Post::to_activity: license error");
@@ -627,7 +627,7 @@ impl Post {
             post.license = license;
         }
 
-        let mut txt_hashtags = md_to_html(&post.source)
+        let mut txt_hashtags = md_to_html(&post.source, "")
             .2
             .into_iter()
             .map(|s| s.to_camel_case())
@@ -889,7 +889,7 @@ impl<'a> FromActivity<LicensedArticle, (&'a Connection, &'a Searcher)> for Post
             }
 
             // save mentions and tags
-            let mut hashtags = md_to_html(&post.source)
+            let mut hashtags = md_to_html(&post.source, "")
                 .2
                 .into_iter()
                 .map(|s| s.to_camel_case())