Add a way to use the admin api without a user.

test/plugs/admin_secret_authentication_plug_test.exs

@@ -0,0 +1,38 @@
+defmodule Pleroma.Plugs.AdminSecretAuthenticationPlugTest do
+  use Pleroma.Web.ConnCase, async: true
+  import Pleroma.Factory
+
+  alias Pleroma.Plugs.AdminSecretAuthenticationPlug
+
+  test "does nothing if a user is assigned", %{conn: conn} do
+    user = insert(:user)
+
+    conn =
+      conn
+      |> assign(:user, user)
+
+    ret_conn =
+      conn
+      |> AdminSecretAuthenticationPlug.call(%{})
+
+    assert conn == ret_conn
+  end
+
+  test "with secret set and given in the 'admin_token' parameter, it assigns an admin user", %{
+    conn: conn
+  } do
+    Pleroma.Config.put(:admin_token, "password123")
+
+    conn =
+      %{conn | params: %{"admin_token" => "wrong_password"}}
+      |> AdminSecretAuthenticationPlug.call(%{})
+
+    refute conn.assigns[:user]
+
+    conn =
+      %{conn | params: %{"admin_token" => "password123"}}
+      |> AdminSecretAuthenticationPlug.call(%{})
+
+    assert conn.assigns[:user].info.is_admin
+  end
+end