Add function to query whether server participates in a room

Move from integer timestamps to datetimes

priv/repo/migrations/20210816144214_change_timestamps_to_datetime.exs

@@ -0,0 +1,15 @@
+defmodule MatrixServer.Repo.Migrations.ChangeTimestampsToDatetime do
+  use Ecto.Migration
+
+  def change do
+    alter table(:events) do
+      remove :origin_server_ts, :integer, null: false
+      add :origin_server_ts, :utc_datetime_usec, null: false
+    end
+
+    alter table(:server_key_info) do
+      remove :valid_until, :bigint, default: 0, null: false
+      add :valid_until, :utc_datetime_usec, null: false
+    end
+  end
+end