Implement devices API (#20)

small improvements

Cargo fmt

Simplify insert and update methods

Review feedback

Remove has_device method calls

Load all devices with a single db call

Remove device as in logout

Put all metadata on the same tree

Create userdevice key fucntion

Implement devices API

Implement all the devices endpoints. There's a couple of pending tasks:

- Integrate the "logout" logic once it lands to master (this should
  remove the given device from the database).
- Track and store last seen timestamp and IP.

Co-authored-by: timokoesters <timo@koesters.xyz>
Co-authored-by: Guillem Nieto <gnieto.talo@gmail.com>

src/database.rs

@@ -56,10 +56,10 @@ impl Database {
             ),
             users: users::Users {
                 userid_password: db.open_tree("userid_password").unwrap(),
-                userdeviceids: db.open_tree("userdeviceids").unwrap(),
                 userid_displayname: db.open_tree("userid_displayname").unwrap(),
                 userid_avatarurl: db.open_tree("userid_avatarurl").unwrap(),
                 userdeviceid_token: db.open_tree("userdeviceid_token").unwrap(),
+                userdeviceid_metadata: db.open_tree("userdeviceid_metadata").unwrap(),
                 token_userdeviceid: db.open_tree("token_userdeviceid").unwrap(),
                 onetimekeyid_onetimekeys: db.open_tree("onetimekeyid_onetimekeys").unwrap(),
                 userdeviceid_devicekeys: db.open_tree("userdeviceid_devicekeys").unwrap(),