api.user_manager: create EmailSender only when required

Convert self._email_sender to an attribute and only create the object
when required.  This way, the API can be run without email support as
long as no endpoints that rely on email features are used.

Signed-off-by: Guillaume Tucker <[email protected]>

api/user_manager.py

@@ -30,13 +30,19 @@ class UserManager(ObjectIDIDMixin, BaseUserManager[User, PydanticObjectId]):
 
     def __init__(self, user_db: BaseUserDatabase[User, PydanticObjectId],
                  password_helper: PasswordHelperProtocol | None = None):
-        self._email_sender = EmailSender()
+        self._email_sender = None
         self._template_env = jinja2.Environment(
                             loader=jinja2.FileSystemLoader(
                                 "./templates/")
                         )
         super().__init__(user_db, password_helper)
 
+    @property
+    def email_sender(self):
+        if self._email_sender is None:
+            self._email_sender = EmailSender()
+        return self._email_sender
+
     async def on_after_register(self, user: User,
                                 request: Optional[Request] = None):
         """Handler to execute after successful user registration"""
@@ -50,7 +56,7 @@ async def on_after_request_verify(self, user: User, token: str,
         content = template.render(
             username=user.username, token=token
         )
-        self._email_sender.create_and_send_email(subject, content, user.email)
+        self.email_sender.create_and_send_email(subject, content, user.email)
 
     async def on_after_verify(self, user: User,
                               request: Optional[Request] = None):
@@ -62,7 +68,7 @@ async def on_after_verify(self, user: User,
         content = template.render(
             username=user.username,
         )
-        self._email_sender.create_and_send_email(subject, content, user.email)
+        self.email_sender.create_and_send_email(subject, content, user.email)
 
     async def on_after_login(self, user: User,
                              request: Optional[Request] = None):
@@ -77,7 +83,7 @@ async def on_after_forgot_password(self, user: User, token: str,
         content = template.render(
             username=user.username, token=token
         )
-        self._email_sender.create_and_send_email(subject, content, user.email)
+        self.email_sender.create_and_send_email(subject, content, user.email)
 
     async def on_after_reset_password(self, user: User,
                                       request: Optional[Request] = None):
@@ -89,7 +95,7 @@ async def on_after_reset_password(self, user: User,
         content = template.render(
             username=user.username,
         )
-        self._email_sender.create_and_send_email(subject, content, user.email)
+        self.email_sender.create_and_send_email(subject, content, user.email)
 
     async def on_after_update(self, user: User, update_dict: Dict[str, Any],
                               request: Optional[Request] = None):