Create a routes constants file and a router for getting routes in app

src/services/router.py

@@ -0,0 +1,19 @@
+from src.constants.routes import Route
+
+
+class Router:
+    def __init__(self, host: str, port: int | None):
+        self._host = host
+        self._port = port
+
+    def interpolate_url[Params](self, route: Route[Params], params: Params, **query_params) -> str:
+        query_strs = []
+        for key, value in query_params.items():
+            query_strs.append(f'{key}={value}')
+
+        query_str = '&'.join(query_strs)
+        query_str = f'?{query_str}' if len(query_str) > 0 else query_str
+        return f'{self._host}{"" if self._port is None else f":{self._port}"}{route.interpolate(params)}{query_str}'
+
+    def get_url(self, route: Route[None], **query_params):
+        return self.interpolate_url(route, None, **query_params)

src/services/users/service.py

@@ -1,3 +1,6 @@
+from src.services.router import Router
+from typing import TypedDict, Unpack
+from src.constants.routes import ROUTES
 from src.services.auth import AuthService, EmailConfirmationClaim, JWT
 from email.headerregistry import Address
 from jinja2 import Environment, PackageLoader, select_autoescape
@@ -23,11 +26,19 @@ def is_valid_password(password: str) -> bool:
     return long_enough and short_enough and has_symbol
 
 
+class ServiceDeps(TypedDict):
+    repo: UserRepo
+    email_service: EmailService
+    auth_service: AuthService
+    router: Router
+
+
 class UserService:
-    def __init__(self, repo: UserRepo, email_service: EmailService, auth_service: AuthService):
-        self._repo = repo
-        self._email_service = email_service
-        self._auth_service = auth_service
+    def __init__(self, **kwargs: Unpack[ServiceDeps]):
+        self._repo = kwargs['repo']
+        self._email_service = kwargs['email_service']
+        self._auth_service = kwargs['auth_service']
+        self._router = kwargs['router']
 
     def login(self, user: UserDTO) -> UserProfile:
         full_user = self._repo.auth_as_user(user)
@@ -66,8 +77,7 @@ class UserService:
         html_template = env.get_template('mail/confirmation_email.html')
         token = self._auth_service.mint_claim_from_user(EmailConfirmationClaim, user)
 
-        # TODO: Parameterize this with configuration that also drives the API
-        url = f'/confirm?token={token}'
+        url = self._router.get_url(ROUTES['confirm_email'], token=token)
         text_content = text_template.render(confirmation_link=url)
         html_content = html_template.render(confirmation_link=url)