feat: add two factor auth (#643)

Add two factor authentication for users who wish to enhance the security of their accounts.

.env.example

@@ -2,6 +2,11 @@
 NEXTAUTH_URL="http://localhost:3000"
 NEXTAUTH_SECRET="secret"
 
+# [[CRYPTO]]
+# Application Key for symmetric encryption and decryption
+# This should be a random string of at least 32 characters
+NEXT_PRIVATE_ENCRYPTION_KEY="CAFEBABE"
+
 # [[AUTH OPTIONAL]]
 NEXT_PRIVATE_GOOGLE_CLIENT_ID=""
 NEXT_PRIVATE_GOOGLE_CLIENT_SECRET=""