Use modern Discord Ui stuff, fix time zones and, fix Dockerfile

Changes:
Use buttons, pagination and modals instead of old text-based stuff
Fix time zones (Closes #23)
Fix Dockerfile
Replace Discord.py with discord-py-interactions
Default time zone is now UTC instead of Europe/Stockholm

Replace
  /remind resume
  /remind pause
  /remind remove
  /remind modify
with
  /remind list

tests/test_countdown.py

@@ -3,6 +3,7 @@
 Jobs are stored in memory.
 """
 import re
+from sched import scheduler
 
 import dateparser
 import pytz
@@ -17,7 +18,8 @@ class TestCountdown:
     """This tests everything.
 
     This sets up sqlite database in memory, changes scheduler timezone
-    to Europe/Stockholm and creates job that runs January 18 2040.
+    to Europe/Stockholm and creates job that runs January 18 2040 and one that
+    runs at 00:00.
     """
 
     jobstores = {"default": SQLAlchemyJobStore(url="sqlite:///:memory")}
@@ -35,8 +37,7 @@ class TestCountdown:
             "TO_TIMEZONE": "Europe/Stockholm",
         },
     )
-
-    run_date = parsed_date.strftime("%Y-%m-%d %H:%M:%S")  # type: ignore
+    run_date = parsed_date.strftime("%Y-%m-%d %H:%M:%S")
     job = scheduler.add_job(
         send_to_discord,
         run_date=run_date,
@@ -47,9 +48,57 @@ class TestCountdown:
         },
     )
 
+    timezone_date = dateparser.parse(
+        "00:00",
+        settings={
+            "PREFER_DATES_FROM": "future",
+            "TO_TIMEZONE": "Europe/Stockholm",
+        },
+    )
+    timezone_run_date = timezone_date.strftime("%Y-%m-%d %H:%M:%S")
+    timezone_job = scheduler.add_job(
+        send_to_discord,
+        run_date=timezone_run_date,
+        kwargs={
+            "channel_id": 865712621109772329,
+            "message": "Running PyTest at 00:00",
+            "author_id": 126462229892694018,
+        },
+    )
+
+    timezone_date2 = dateparser.parse(
+        "13:37",
+        settings={
+            "PREFER_DATES_FROM": "future",
+            "TO_TIMEZONE": "Europe/Stockholm",
+        },
+    )
+    timezone_run_date2 = timezone_date2.strftime("%Y-%m-%d %H:%M:%S")
+    timezone_job2 = scheduler.add_job(
+        send_to_discord,
+        run_date=timezone_run_date2,
+        kwargs={
+            "channel_id": 865712621109772329,
+            "message": "Running PyTest at 13:37",
+            "author_id": 126462229892694018,
+        },
+    )
+
     def test_countdown(self):
         """Check if calc_countdown returns days, hours and minutes."""
         # FIXME: This will break when there is 0 seconds/hours/days left
         pattern = re.compile(r"\d* (day|days), \d* (hour|hours). \d* (minute|minutes)")
         countdown = calculate(self.job)
         assert pattern.match(countdown)
+
+    def test_if_timezones_are_working(self):
+        """Check if timezones are working."""
+        time_job = self.scheduler.get_job(self.timezone_job.id)
+        assert time_job.trigger.run_date.hour == 0
+        assert time_job.trigger.run_date.minute == 0
+        assert time_job.trigger.run_date.second == 0
+
+        time_job2 = self.scheduler.get_job(self.timezone_job2.id)
+        assert time_job2.trigger.run_date.hour == 13
+        assert time_job2.trigger.run_date.minute == 37
+        assert time_job2.trigger.run_date.second == 0