Add functionality for drawing folium.Maps

- this code is not unit-tested due to the complexity involving
  interactive `folium.Map`s => visual checks give high confidence

src/urban_meal_delivery/db/restaurants.py

@@ -1,8 +1,13 @@
 """Provide the ORM's `Restaurant` model."""
 
+from __future__ import annotations
+
+import folium
 import sqlalchemy as sa
 from sqlalchemy import orm
 
+from urban_meal_delivery import config
+from urban_meal_delivery import db
 from urban_meal_delivery.db import meta
 
 
@@ -45,3 +50,92 @@ class Restaurant(meta.Base):
     def __repr__(self) -> str:
         """Non-literal text representation."""
         return '<{cls}({name})>'.format(cls=self.__class__.__name__, name=self.name)
+
+    def clear_map(self) -> Restaurant:  # pragma: no cover
+        """Shortcut to the `.address.city.clear_map()` method.
+
+        Returns:
+            self: enabling method chaining
+        """  # noqa:D402,DAR203
+        self.address.city.clear_map()
+        return self
+
+    @property  # pragma: no cover
+    def map(self) -> folium.Map:  # noqa:WPS125
+        """Shortcut to the `.address.city.map` object."""
+        return self.address.city.map
+
+    def draw(  # noqa:WPS231
+        self, customers: bool = True, order_counts: bool = False,  # pragma: no cover
+    ) -> folium.Map:
+        """Draw the restaurant on the `.address.city.map`.
+
+        By default, the restaurant's delivery locations are also shown.
+
+        Args:
+            customers: show the restaurant's delivery locations
+            order_counts: show the number of orders at the delivery locations;
+                only useful if `customers=True`
+
+        Returns:
+            `.address.city.map` for convenience in interactive usage
+        """
+        if customers:
+            # Obtain all primary `Address`es in the city that
+            # received at least one delivery from `self`.
+            delivery_addresses = (  # noqa:ECE001
+                db.session.query(db.Address)
+                .filter(
+                    db.Address.id.in_(
+                        db.session.query(db.Address.primary_id)  # noqa:WPS221
+                        .join(db.Order, db.Address.id == db.Order.delivery_address_id)
+                        .filter(db.Order.restaurant_id == self.id)
+                        .distinct()
+                        .all(),
+                    ),
+                )
+                .all()
+            )
+
+            for address in delivery_addresses:
+                if order_counts:
+                    n_orders = (  # noqa:ECE001
+                        db.session.query(db.Order)
+                        .join(db.Address, db.Order.delivery_address_id == db.Address.id)
+                        .filter(db.Order.restaurant_id == self.id)
+                        .filter(db.Address.primary_id == address.id)
+                        .count()
+                    )
+                    if n_orders >= 25:
+                        radius = 20  # noqa:WPS220
+                    elif n_orders >= 10:
+                        radius = 15  # noqa:WPS220
+                    elif n_orders >= 5:
+                        radius = 10  # noqa:WPS220
+                    elif n_orders > 1:
+                        radius = 5  # noqa:WPS220
+                    else:
+                        radius = 1  # noqa:WPS220
+
+                    address.draw(
+                        radius=radius,
+                        color=config.CUSTOMER_COLOR,
+                        fill_color=config.CUSTOMER_COLOR,
+                        fill_opacity=0.3,
+                        tooltip=f'n_orders={n_orders}',
+                    )
+
+                else:
+                    address.draw(
+                        radius=1, color=config.CUSTOMER_COLOR,
+                    )
+
+        self.address.draw(
+            radius=20,
+            color=config.RESTAURANT_COLOR,
+            fill_color=config.RESTAURANT_COLOR,
+            fill_opacity=0.3,
+            tooltip=f'{self.name} (#{self.id}) | n_orders={len(self.orders)}',
+        )
+
+        return self.map