Update the test configuration to allow run server during tests.

test/support/test_endpoints.ex

@@ -0,0 +1,12 @@
+defmodule DecentralisedBookIndex.TestEndpoints do
+  @moduledoc "Test API endpoint for tests"
+
+  @test_api_endpoint "http://localhost:4002"
+
+  @doc """
+  Returns the url of test API endpoint.
+  """
+  def test_api_endpoint(_opts \\ []) do
+    @test_api_endpoint
+  end
+end