Add alias creation endpoint

lib/matrix_server/alias.ex

@@ -0,0 +1,28 @@
+defmodule MatrixServer.Alias do
+  use Ecto.Schema
+
+  import Ecto.Changeset
+
+  alias MatrixServer.{Repo, Alias, Room}
+  alias Ecto.Changeset
+
+  @primary_key {:alias, :string, []}
+  schema "aliases" do
+    belongs_to :room, Room, foreign_key: :room_id, references: :id, type: :string
+  end
+
+  def create(alias, room_id) do
+    change(%Alias{}, alias: alias, room_id: room_id)
+    |> assoc_constraint(:room)
+    |> unique_constraint(:alias, name: :aliases_pkey)
+    |> Repo.insert()
+  end
+
+  def get_error(%Changeset{errors: [error | _]}), do: get_error(error)
+  def get_error({:alias, {_, [{:constraint, :unique} | _]}}), do: :room_alias_exists
+
+  def get_error({:room, {_, [{:constraint, :assoc} | _]}}),
+    do: {:not_found, "The room was not found."}
+
+  def get_error(_), do: :bad_json
+end

lib/matrix_server/room.ex

@@ -4,7 +4,7 @@ defmodule MatrixServer.Room do
   import Ecto.Changeset
   import Ecto.Query
 
-  alias MatrixServer.{Repo, Room, Event, RoomServer}
+  alias MatrixServer.{Repo, Room, Event, Alias, RoomServer}
   alias MatrixServerWeb.API.CreateRoom
 
   @primary_key {:id, :string, []}
@@ -13,6 +13,7 @@ defmodule MatrixServer.Room do
     field :state, {:array, {:array, :string}}
     field :forward_extremities, {:array, :string}
     has_many :events, Event, foreign_key: :event_id
+    has_many :aliases, Alias, foreign_key: :room_id
   end
 
   def changeset(room, params \\ %{}) do