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-front/src/modules/object-metadata/hooks/__mocks__/useFieldMetadataItem.ts

@@ -158,6 +158,7 @@ export const queries = {
         isPasswordAuthEnabled
         subdomain
         hasValidEnterpriseKey
+        hostname
         featureFlags {
           id
           key
@@ -307,6 +308,7 @@ export const responseData = {
         isMicrosoftAuthEnabled: false,
         isPasswordAuthEnabled: true,
         subdomain: 'test',
+        hostname: null,
         featureFlags: [],
         metadataVersion: 1,
         currentBillingSubscription: null,