Improve holidays config form and naming (#133663)

The holidays library is improving over time, let's make use of their
data for a more user-friendly experience.

Co-authored-by: G Johansson <goran.johansson@shiftit.se>

homeassistant/components/holiday/config_flow.py

@@ -19,6 +19,7 @@ from homeassistant.core import callback
 from homeassistant.helpers.selector import (
     CountrySelector,
     CountrySelectorConfig,
+    SelectOptionDict,
     SelectSelector,
     SelectSelectorConfig,
     SelectSelectorMode,
@@ -30,6 +31,30 @@ from .const import CONF_CATEGORIES, CONF_PROVINCE, DOMAIN
 SUPPORTED_COUNTRIES = list_supported_countries(include_aliases=False)
 
 
+def get_optional_provinces(country: str) -> list[Any]:
+    """Return the country provinces (territories).
+
+    Some territories can have extra or different holidays
+    from another within the same country.
+    Some territories can have different names (aliases).
+    """
+    province_options: list[Any] = []
+
+    if provinces := SUPPORTED_COUNTRIES[country]:
+        country_data = country_holidays(country, years=dt_util.utcnow().year)
+        if country_data.subdivisions_aliases and (
+            subdiv_aliases := country_data.get_subdivision_aliases()
+        ):
+            province_options = [
+                SelectOptionDict(value=k, label=", ".join(v))
+                for k, v in subdiv_aliases.items()
+            ]
+        else:
+            province_options = provinces
+
+    return province_options
+
+
 def get_optional_categories(country: str) -> list[str]:
     """Return the country categories.
 
@@ -45,7 +70,7 @@ def get_optional_categories(country: str) -> list[str]:
 def get_options_schema(country: str) -> vol.Schema:
     """Return the options schema."""
     schema = {}
-    if provinces := SUPPORTED_COUNTRIES[country]:
+    if provinces := get_optional_provinces(country):
         schema[vol.Optional(CONF_PROVINCE)] = SelectSelector(
             SelectSelectorConfig(
                 options=provinces,