v2.1.0: Refactoring, accuracy improvements and a more accessible interface
==========================================================================

- Possibly breaking changes:

  - The 'Space' column has been renamed to 'Distance' as this makes more sense

  - :func:`fastf1.utils.delta_time` now returns two values; see explanation in the documentation

  - Lap telemetry is no longer precalculated and no longer saved in a separate column of the :class:`Laps` DataFrame.
    This telemetry is now a computed property of :class:`Laps` and :class:`Lap`

    - calculated property `.telemetry`: This contains position and car data merged into one instance of
      :class:`Telemetry` (instance of `DataFrame`). The data is comparable to the previous 'telemetry' column.
      This data is intended for easy plotting. It should not be used for any further calculations as it
      contains interpolated values.

      .. code-block::

        laps = session.load_laps()
        fastest = laps.pick_fastest()

        tel = fastest['telemetry']  # will now fail as telemetry is no longer saved in DataFrame/Series
        tel = fastest.telemetry  # will (still) work as this now accesses the computed property

    - function `get_car_data`, `get_pos_data`: These functions are available for :class:`Lap` and :class:`Laps`.
      They return the telemetry data as received from the api with minimal postprocessing and crucially
      unmerged and without any interpolated values. This data should be used if you intend to do any further
      calculations with it.

      Also read the new documentation section about doing accurate calculations: :ref:`howto_accurate_calculations`

  - Patches and color scheme changes which were automatically applied when importing :mod:`fastf1.plotting`
    now need to be enabled explicitly. This is done by calling :func:`fasf1.plotting.setup_mpl`.
    This function offers configuration through keyword arguments. The defaults are equal to what was done
    automatically before.
    It is highly recommended that you call this function to set up your matplotlib plotting environment.

  - The formatting of timedelta values in matplotlib plots is now handled by an external module called 'Timple'.
    As part of this change, the function :func:`fastf1.plotting.laptime_axis` has been removed. Timedelta data
    is now detected automatically if matplotlib timedelta support is enabled through :func:`fastf1.plotting.setup_mpl`.
    This will hopefully make the plotting of timedelta values considerably more reliable.

  - The computed telemetry channels 'Distance' (before: 'Space'), 'DriverAhead' and 'DistanceToDriverAhead' are no
    longer added to the telemetry data by default. This is done for speed and accuracy reasons. These channels can now
    be added by calling the appropriate :meth:`Telemetry.add_*` methods of the new :class:`fastf1.core.Telemetry` class.

  - The cache has been completely rewritten. It is now fully supported again and can detect version updates which
    require updating the cached data.
    Enabling the cache is now done using :func:`fastf1.api.Cache.enable_cache`



- Changes:
  - Accuracy improvement: Changes to some parts of the general flow of processing data to reduce calculation errors

  - Accuracy improvement: slightly better determination of the time at which a lap starts

  - Speed improvement: Faster parsing of API data

  - Added track status information to laps data

  - Added lap accuracy validation as a boolean 'IsAccurate' value for each lap. This is set based on track status,
    availability of some required lap data, pit stops

  - Added 'Source' to telemetry data to indicate whether a value is original ('car' or 'pos' depending on source)
    or interpolated

  - Added the class :class:`fastf1.core.Lap` which subclasses :class:`pd.Series`. :class:`Lap` is now the result of
    slicing :class:`fastf1.core.Laps`.

  - Added additional `pick_*()` functions to :class:`fastf1.core.Laps`

  - Added :class:`fastf1.core.Telemetry` which subclasses :class:`pd.DataFrame`. This class offers various methods
    for working with the telemetry data and should make it easier to work with the data. Previously inaccessible
    functionality is now accessible in a more DataFrame-like style.

  - Added various slicing capabilities for :class:`fastf1.core.Telemetry`

  - Telemetry data can be sliced at any point and calculated telemetry channels (Distance, Driver Ahead, ...)
    can be added to this slice specifically.

    Example usages:

      - 'Distance' can be calculated continuously over multiple laps (starts at zero on the first lap
        and increases all the time).

      - 'DriverAhead' can now be calculated for small telemetry slices more efficiently

  - DistanceToDriverAhead is reimplemented and returns a considerably smoother result now. This is at the cost of
    increasing integration error when used over longer periods of time (i.e. over multiple laps). To work around this,
    it should be applied to laps individually. Additionally, the old implementation is still available in
    :mod:`fastf1.legacy`.

  - Add a SignalR client for receiving and saving live timing and telemetry data during a session.


- Fixed:
  - fix: SessionNotAvailableError is now raised as Exception instead of BaseException

  - fix a crash when there is no valid car telemetry data at all (2019, Australia, FP3)

  - fix a crash caused by the resampling progressbar when there are very few laps in a session (2019, Azerbaijan, FP1)

  - fix a crash in _inject_position when some telemetry data is missing (2019, Silverstone, FP1)

  - fix a crash when data for a session can be requested but the data does not contain any useful values at
    all (2020, Styria, 'FP3')