Restructure code and use APScheduler for daemon functionality

app/email.py

@@ -1,27 +1,27 @@
-from flask import current_app, render_template
+from app import mail
+from flask import current_app, Flask, render_template
 from flask_mail import Message
-from typing import Any, Text
-from . import mail
-from .decorators import background
+from threading import Thread
+from typing import Any
 
 
-def create_message(
-    recipient: str,
-    subject: str,
-    template: str,
-    **kwargs: Any
-) -> Message:
+def create_message(recipient: str, subject: str, template: str, **kwargs: Any) -> Message:
     subject_prefix: str = current_app.config['NOPAQUE_MAIL_SUBJECT_PREFIX']
     msg: Message = Message(
-        f'{subject_prefix} {subject}',
-        recipients=[recipient]
+        body=render_template(f'{template}.txt.j2', **kwargs),
+        html=render_template(f'{template}.html.j2', **kwargs),
+        recipients=[recipient],
+        subject=f'{subject_prefix} {subject}'
     )
-    msg.body = render_template(f'{template}.txt.j2', **kwargs)
-    msg.html = render_template(f'{template}.html.j2', **kwargs)
     return msg
 
 
-@background
-def send(msg: Message, *args, **kwargs):
-    with kwargs['app'].app_context():
+def _send(app: Flask, msg):
+    with app.app_context():
         mail.send(msg)
+
+
+def send(msg: Message, *args, **kwargs):
+    thread = Thread(target=_send, args=[current_app._get_current_object(), msg])
+    thread.start()
+    return thread