Uploading an avatar media exceeding max size returns a 413

Until now it was returning a 500 because the upload plug were going
through the changeset and ending in the JSON encoder, which raised
because struct has to @derive the encoder.

lib/pleroma/user.ex

@@ -611,7 +611,13 @@ defmodule Pleroma.User do
          {:ok, new_value} <- value_function.(value) do
       put_change(changeset, map_field, new_value)
     else
-      _ -> changeset
+      {:error, :file_too_large} ->
+        Ecto.Changeset.validate_change(changeset, map_field, fn map_field, _value ->
+          [{map_field, "file is too large"}]
+        end)
+
+      _ ->
+        changeset
     end
   end
 

lib/pleroma/web/api_spec/operations/account_operation.ex

@@ -64,7 +64,8 @@ defmodule Pleroma.Web.ApiSpec.AccountOperation do
       requestBody: request_body("Parameters", update_credentials_request(), required: true),
       responses: %{
         200 => Operation.response("Account", "application/json", Account),
-        403 => Operation.response("Error", "application/json", ApiError)
+        403 => Operation.response("Error", "application/json", ApiError),
+        413 => Operation.response("Error", "application/json", ApiError)
       }
     }
   end

lib/pleroma/web/mastodon_api/controllers/account_controller.ex

@@ -254,7 +254,11 @@ defmodule Pleroma.Web.MastodonAPI.AccountController do
         with_pleroma_settings: true
       )
     else
-      _e -> render_error(conn, :forbidden, "Invalid request")
+      {:error, %Ecto.Changeset{errors: [avatar: {"file is too large", _}]}} ->
+        render_error(conn, :request_entity_too_large, "File is too large")
+
+      _e ->
+        render_error(conn, :forbidden, "Invalid request")
     end
   end