Remove deprecated functions

[Florian Kotthoff]

Several warnings appear when we run pytests:

• test_utils_write_to_database.py:169: FutureWarning: Mismatched null-like values nan and None found. In a future version, pandas equality-testing functions (e.g. assert_frame_equal) will consider these not-matching and raise.
  pd.testing.assert_frame_equal(df_edited, df_correct)

• DeprecationWarning: datetime.datetime.utcfromtimestamp() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.fromtimestamp(timestamp, datetime.UTC).
  if rate and total else datetime.utcfromtimestamp(0))

• zeep\cache.py:172: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
  now = datetime.datetime.utcnow().replace(tzinfo=pytz.utc)

• zeep\cache.py:157: DeprecationWarning: The default timestamp converter is deprecated as of Python 3.12; see the sqlite3 documentation for suggested replacement recipes
  rows = cursor.fetchall()

• open_mastr\utils\orm.py:17: MovedIn20Warning: The declarative_base() function is now available as sqlalchemy.orm.declarative_base(). (deprecated since: 2.0) (Background on SQLAlchemy 2.0 at: https://sqlalche.me/e/b8d9)
  Base = declarative_base(metadata=meta)

• zeep\utils.py:1: DeprecationWarning: 'cgi' is deprecated and slated for removal in Python 3.13
  import cgi

  Maybe one of these warnings is reltated to #497

[Florian Kotthoff]

All zeep warnings are dependencies from within zeep and need to fixed there.

[Florian Kotthoff]

the function declarative_base is now a class: DeclerativeBase -> see https://docs.sqlalchemy.org/en/20/orm/quickstart.html