Fix support for special characters in various environment variables (#35314)

Co-authored-by: Matt Jankowski <matt@jankowski.online>

spec/configuration/email_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Configuration for email', type: :feature do
+  context 'with special characters in SMTP_PASSWORD env variable' do
+    let(:password) { ']]123456789[["!:@<>/\\=' }
+
+    around do |example|
+      ClimateControl.modify SMTP_PASSWORD: password do
+        example.run
+      end
+    end
+
+    it 'parses value correctly' do
+      expect(Rails.application.config_for(:email, env: :production))
+        .to include(
+          smtp_settings: include(password: password)
+        )
+    end
+  end
+end