feat(signup): allow to block signup (#3209)

* feat(signup): allow to block signup

* feat(signup): update environment variable documentation

* test: update auth service tests

* feat(signup): prevent user from reaching out the sign up page

* Fix lint

* Fixes

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Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-docs/docs/start/self-hosting/environment-variables.mdx

@@ -56,6 +56,7 @@ import TabItem from '@theme/TabItem';
     ['AUTH_GOOGLE_CLIENT_SECRET', '', 'Google client secret'],
     ['AUTH_GOOGLE_CALLBACK_URL', '', 'Google auth callback'],
     ['FRONT_AUTH_CALLBACK_URL', 'http://localhost:3001/verify ', 'Callback used for Login page'],
+    ['IS_SIGN_UP_DISABLED', 'false', 'Disable sign-up'],
     ]}></OptionTable>
 
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