Fix common bug in parsing of UTC datetimes; remove dateutil

[probberechts]

This PR addresses a common bug related to parsing UTC datetimes, fixes the timezone of Opta F24 data and removes the dateutil dependency.

The following conventions are used:

• All datetimes are timezone-aware
• If the local timezone is known, the local timezone is used
• If the local timezone is not known, UTC is used

astimezone -> replace

Often, datetimes are specified as a string and use the UTC timezone. In kloppy, we want to parse these a timezone-aware datetime. Then, then string was usually parsed and converted to a timezone-aware datetime as follows:

>>> parse("2024-12-14 12:00").astimezone(timezone.utc)
datetime.datetime(2024, 12, 14, 11, 0, tzinfo=datetime.timezone.utc)  # on a system with local timezone UTC+1

The correct implementation is:

>>> parse("2024-12-14 12:00").replace(tzinfo=timezone.utc)
datetime.datetime(2024, 12, 14, 12, 0, tzinfo=datetime.timezone.utc)

The former changes the timezone, while the latter sets the timezone (i.e., makes the datetime timezone-aware).

Opta F24 timezone

According to the documentation, timestamps in the F24 files use the timezone "Europe/London".

Remove dateutil

We know the exact format of the date string in advance. Hence, we don't need dateutil's parser module.

[probberechts]

Is there a one-minute difference between UK/London and UTC? Or did I make a mistake?

import datetime
from pytz import timezone

naive_datetime = datetime.datetime.now()
local_datetime = naive_datetime.replace(tzinfo=timezone('Europe/London'))
utc_datetime = local_datetime.astimezone(timezone('UTC'))
print("Naive datetime:", naive_datetime)
print("Local datetime:", local_datetime)
print("UTC datetime:  ", utc_datetime)

This is the output:

Naive datetime: 2024-12-14 21:53:04.383850
Local datetime: 2024-12-14 21:53:04.383850-00:01
UTC datetime:   2024-12-14 21:54:04.383850+00:00

Update: I've figured it out: one should use localize instead of replace. See https://groups.google.com/g/django-users/c/rXalwEztfr0/m/QAd5bIJubwAJ. I'll update the code later.