feat: Enforce single team when self-hosted (#1954)

* fix: Enforce single team when self hosting

* test: positive case

* refactor

* fix: Visible error message on login screen for max teams scenario

* Update Notices.js

* lint

server/test/helper.js

@@ -6,6 +6,8 @@ process.env.DATABASE_URL = process.env.DATABASE_URL_TEST;
 process.env.NODE_ENV = "test";
 process.env.GOOGLE_CLIENT_ID = "123";
 process.env.SLACK_KEY = "123";
+process.env.DEPLOYMENT = "";
+process.env.ALLOWED_DOMAINS = "allowed-domain.com";
 
 // This is needed for the relative manual mock to be picked up
 jest.mock("../events");