Big repository reorganization

The code is divided in three crates:
- plume-common, for the ActivityPub module, and some common utils
- plume-models, for the models and database-related code
- plume, the app itself

This new organization will allow to test it more easily, but also to create other tools that only reuse a little part of
the code (for instance a Wordpress import tool, that would just use the plume-models crate)

src/inbox.rs

@@ -0,0 +1,66 @@
+use activitypub::activity::{Announce, Create, Like, Undo};
+use diesel::PgConnection;
+use failure::Error;
+use serde_json;
+
+use plume_common::activity_pub::{Id, inbox::{Deletable, FromActivity, InboxError}};
+use plume_models::{
+    comments::Comment,
+    follows::Follow,
+    instance::Instance,
+    likes,
+    reshares::Reshare,
+    posts::Post,
+    users::User
+};
+
+pub trait Inbox {
+    fn received(&self, conn: &PgConnection, act: serde_json::Value) -> Result<(), Error> {
+        let actor_id = Id::new(act["actor"].as_str().unwrap());
+        match act["type"].as_str() {
+            Some(t) => {
+                match t {
+                    "Announce" => {
+                        Reshare::from_activity(conn, serde_json::from_value(act.clone())?, actor_id);
+                        Ok(())
+                    },
+                    "Create" => {
+                        let act: Create = serde_json::from_value(act.clone())?;
+                        if Post::try_from_activity(conn, act.clone()) || Comment::try_from_activity(conn, act) {
+                            Ok(())
+                        } else {
+                            Err(InboxError::InvalidType)?
+                        }
+                    },
+                    "Follow" => {
+                        Follow::from_activity(conn, serde_json::from_value(act.clone())?, actor_id);
+                        Ok(())
+                    },
+                    "Like" => {
+                        likes::Like::from_activity(conn, serde_json::from_value(act.clone())?, actor_id);
+                        Ok(())
+                    },
+                    "Undo" => {
+                        let act: Undo = serde_json::from_value(act.clone())?;
+                        match act.undo_props.object["type"].as_str().unwrap() {
+                            "Like" => {
+                                likes::Like::delete_activity(conn, Id::new(act.undo_props.object_object::<Like>()?.object_props.id_string()?));
+                                Ok(())
+                            },
+                            "Announce" => {
+                                Reshare::delete_activity(conn, Id::new(act.undo_props.object_object::<Announce>()?.object_props.id_string()?));
+                                Ok(())
+                            }
+                            _ => Err(InboxError::CantUndo)?
+                        }
+                    }
+                    _ => Err(InboxError::InvalidType)?
+                }
+            },
+            None => Err(InboxError::NoType)?
+        }
+    }
+}
+
+impl Inbox for Instance {}
+impl Inbox for User {}