feat(security): add approved rooms/users/domains as env variables (#277)

* feat(security): add approved rooms/users/domains as env variables
* chore(lint): fix R0902
* chore(lint): fix C0114
* chore(lint): fix C0116
* chore(lint): fix C0413

tests/test_helpers.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+
+"""Provides test cases for app/utils/helpers.py."""
+
+from app.utils.helpers import validate_email_syntax  # pragma: no cover
+
+
+def test_validate_email_syntax_true() -> None:
+    """Test validate_email_syntax() with a real email address."""
+    email: str = "test@test.com"
+    assert validate_email_syntax(email)
+
+
+def test_validate_email_syntax_false1() -> None:
+    """Test validate_email_syntax() with an invalid email address."""
+    email: str = "test@test"
+    assert not validate_email_syntax(email)
+
+
+def test_validate_email_syntax_false2() -> None:
+    """Test validate_email_syntax() with an invalid email address."""
+    email: str = "test"
+    assert not validate_email_syntax(email)