Create multi page layout (#147)

Created two pages (home and company), page reloads after company
selection in dropdown or clicking the home button.

tests/ui/app_test.py

@@ -0,0 +1,33 @@
+"""Test for the main app dashboard."""
+from collections.abc import Generator
+
+import pytest
+from sqlalchemy.orm import Session
+
+from aki_prj23_transparenzregister.ui import app
+from aki_prj23_transparenzregister.ui.session_handler import SessionHandler
+
+
+@pytest.fixture(autouse=True)
+def _set_session(full_db: Session) -> Generator[None, None, None]:
+    """Sets a session for the dash application to be used."""
+    SessionHandler.session = full_db
+    yield
+    SessionHandler.session = None
+
+
+def test_import() -> None:
+    """Checks if an import of the dash app can be made."""
+    assert app is not None
+
+
+def test_go_to_home() -> None:
+    """Checks if the go_to_home callback yields a result."""
+    output = app.go_to_home(1)
+    assert output == "/"
+
+
+def test_go_to_company_page() -> None:
+    """Checks if the go_to_company_page callback yields a result."""
+    output = app.go_to_company_page(1)
+    assert output == "/Unternehmensdetails/1"