Implement access token authentication

Add whoami endpoint

priv/repo/migrations/20210623145023_add_devices_table.exs

@@ -13,6 +13,7 @@ defmodule MatrixServer.Repo.Migrations.AddDevicesTable do
           null: false
     end
 
+    # Compound primary already indexes device_id.
     create index(:devices, [:localpart])
   end
 end

priv/repo/migrations/20210625205812_add_access_token_index_to_devices.exs

@@ -0,0 +1,7 @@
+defmodule MatrixServer.Repo.Migrations.AddAccessTokenIndexToDevices do
+  use Ecto.Migration
+
+  def change do
+    create index(:devices, [:access_token], unique: true)
+  end
+end