feat: add option to duplicate existing lighting instance (#1329)

* feat: add option to duplicate existing lighting instance

A menu step in the config flow was added that allows a user to create a
new instance or duplicate the options of an existing one.

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* Add type annotation, tests, and translations for duplicate feature

- Add type annotation for source_options class attribute
- Add menu step translations to en.json
- Add tests for menu display, new instance creation, and duplication

* Simplify source_options access with class-level default

---------
Co-authored-by: Bas Nijholt <bas@nijho.lt>

tests/test_config_flow.py

@@ -145,3 +145,105 @@ async def test_options_flow_for_yaml_import(hass):
     assert result["type"] == FlowResultType.FORM
     assert result["step_id"] == "init"
     assert result.get("data_schema") is None
+
+
+async def test_menu_shown_when_entries_exist(hass):
+    """Test that menu step is shown when existing entries exist."""
+    # Create an existing entry
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        title="existing",
+        data={CONF_NAME: "existing"},
+        options={"min_brightness": 10},
+    )
+    entry.add_to_hass(hass)
+
+    # Start a new config flow - should show menu
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN,
+        context={"source": "user"},
+    )
+
+    assert result["type"] == FlowResultType.FORM
+    assert result["step_id"] == "menu"
+
+
+async def test_menu_create_new_instance(hass):
+    """Test creating a new instance through the menu."""
+    # Create an existing entry
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        title="existing",
+        data={CONF_NAME: "existing"},
+        options={"min_brightness": 10},
+    )
+    entry.add_to_hass(hass)
+
+    # Start config flow - shows menu
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN,
+        context={"source": "user"},
+    )
+    assert result["step_id"] == "menu"
+
+    # Choose to create new instance
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={"action": "new"},
+    )
+
+    # Should show name form
+    assert result["type"] == FlowResultType.FORM
+    assert result["step_id"] == "user"
+
+    # Enter name
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={CONF_NAME: "new instance"},
+    )
+
+    assert result["type"] == FlowResultType.CREATE_ENTRY
+    assert result["title"] == "new instance"
+    # New instance should have no options (not duplicated)
+    assert result["options"] == {}
+
+
+async def test_menu_duplicate_instance(hass):
+    """Test duplicating an existing instance through the menu."""
+    # Create an existing entry with custom options
+    source_options = {"min_brightness": 20, "max_brightness": 80}
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        title="source",
+        data={CONF_NAME: "source"},
+        options=source_options,
+    )
+    entry.add_to_hass(hass)
+
+    # Start config flow - shows menu
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN,
+        context={"source": "user"},
+    )
+    assert result["step_id"] == "menu"
+
+    # Choose to duplicate existing entry
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={"action": entry.entry_id},
+    )
+
+    # Should show name form
+    assert result["type"] == FlowResultType.FORM
+    assert result["step_id"] == "user"
+
+    # Enter name for duplicated instance
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={CONF_NAME: "duplicated"},
+    )
+
+    assert result["type"] == FlowResultType.CREATE_ENTRY
+    assert result["title"] == "duplicated"
+    # Duplicated instance should have copied options
+    assert result["options"] == source_options