Log successful and failed login attempts in a separate log file

We log the login parameter and the request IP address.

Quoting the ENS:

> [op.acc.5.r5.1] Se registrarán los accesos con éxito y los fallidos.

spec/lib/authentication_logger_spec.rb

@@ -0,0 +1,41 @@
+require "rails_helper"
+
+describe AuthenticationLogger do
+  describe ".path" do
+    context "when multitenancy is disabled" do
+      before { allow(Rails.application.config).to receive(:multitenancy).and_return(false) }
+
+      it "uses default file" do
+        expect(AuthenticationLogger.path).to eq(Rails.root.join("log", "authentication.log"))
+      end
+    end
+
+    context "when multitenancy is enabled" do
+      before { allow(Rails.application.config).to receive(:multitenancy).and_return(true) }
+
+      it "uses the default file for the public schema" do
+        Tenant.switch("public") do
+          path = Rails.root.join("log", "authentication.log")
+
+          expect(AuthenticationLogger.path).to eq(path)
+        end
+      end
+
+      it "uses a separate file for any other tenant" do
+        create(:tenant, schema: "tenant1")
+        Tenant.switch("tenant1") do
+          path = Rails.root.join("log", "tenants", "tenant1", "authentication.log")
+
+          expect(AuthenticationLogger.path).to eq(path)
+        end
+
+        create(:tenant, schema: "tenant2")
+        Tenant.switch("tenant2") do
+          path = Rails.root.join("log", "tenants", "tenant2", "authentication.log")
+
+          expect(AuthenticationLogger.path).to eq(path)
+        end
+      end
+    end
+  end
+end