feat(custom-domains): allow to register a custom domain (without UI) (#9879)

# In this PR
- Allow to register a custom domain
- Refacto subdomain generation

# In other PRs
- Add UI to deal with a custom domain
- Add logic to work with custom domain

packages/twenty-server/.env.example

@@ -77,4 +77,6 @@ FRONT_PORT=3001
 # SESSION_STORE_SECRET=replace_me_with_a_random_string_session
 # ENTERPRISE_KEY=replace_me_with_a_valid_enterprise_key
 # SSL_KEY_PATH="./certs/your-cert.key"
-# SSL_CERT_PATH="./certs/your-cert.crt"
+# SSL_CERT_PATH="./certs/your-cert.crt"
+# CLOUDFLARE_API_KEY=
+# CLOUDFLARE_ZONE_ID=