Also
- Adds typing to, adds doc to and renames parameters of:
  - some private `ExchangeCalendar` initialization methods.
  - some private `XKRXExchangeCalendar` initialization methods.
  - `pandas_utils.days_at_time`.

Fixes warnings:
- pandas `union_many` deprecated.
- `pd.Series.append` deprecated.
- writting to a copy of an array (pandas).

Also:
- adds `indexes_union` function to `pandas_utils`.
- adds doctests in `pandas_utils` to test suite.

Fixes bug that included close (wrongly) when `force` was True,
`intervals` was False and closed was `left` or `neither`. Revises test.

Revises so that `start` and `end` can be passed as either date or
minute. Adds `TestTradingIndex.test_start_end_times`.

Updates tutorial `trading_index.ipynb`.

Also:
- adds following functions to `calendar_helpers` and associated
test(s) to `test_calendar_helpers`:
  - `is_date`
  - `to_utc`
  - `parse_date_or_minute`

Revises following `ExchangeCalendar` methods, and associated tests,
so that `count` parameter reflects window length (previously window
length was `count` + 1):
- `sessions_window`.
- `minutes_window`.

Also changes methods' parameter names:
- `start_dt` renamed `minute`.
- `session_label` renamed `session`.

Changes error raised when prev or next minute or session is
out-of-bounds. Changed from `ValueError` to `Requested*OutOfBounds`.

Simplifies minute_to_*_session methods.

Changes `ExchangeCalendar` bound* and default* properties to class
methods.

To support change also makes
`PrecomputedExchangeCalendar.precomputed_holidays` a class method.

Renames following `ExchangeCalendar.schedule` columns:
- 'market_open' renamed 'open'
- 'market_close' renamed 'close'

Renames parameters of following `ExchangeCalendar` methods (as #61):
- `session_open`
- `session_close`
- `session_break_start`
- `session_break_end`
- `sessions_in_range`
- `is_session`
- `is_open_on_minute`
- `previous_open`
- `pervious_close`
- `next_open`
- `next_close`
- `previous_minute`
- `next_minute`

Deprecates following `ExchangeCalendar` methods:
- `sessions_opens` (use .opens[start, end] instead).
- `sessions_closes` (use .closes[start, end] instead).

Removes following `ExchangeCalendar` methods deprecated in v3.4:
- `execution_minutes_for_session`
- `execution_minutes_for_sessions_in_range`
- `execution_time_from_open`
- `execution_time_from_close`
- `previous_session_label`
- `next_session_label`
- `date_to_session_label`
- `minute_to_session_label`
- `open_and_close_for_session`
- `break_start_and_end_for_session`
- `minutes_for_session`
- `session_opens_in_range`
- `session_closes_in_range`
- `minutes_for_sessions_in_range`
- `minutes_count_for_sessions_in_range`
- `session_distance`
- `minute_index_to_session_labels`
- `all_sessions`
- `all_minutes`
- `all_minutes_nanos`
- `first_trading_minute`
- `last_trading_minute`
- `first_trading_session`
- `last_trading_session`
- `has_breaks`
- `market_opens_nanos`
- `market_closes_nanos`
- `market_break_starts_nanos`
- `market_break_ends_nanos`

- Replaces`@lazyval` with `@functools.cached_property`
- Replaces `@functools.lru_cache` with `@functools.cached_property`
where lru_cache was decorating a 'would-be' property.
- Introduces Literal type annotation.
- Removes 3.7 from test and build workflow.
- Sets test and build workflow to run on 3.8 and 3.10 (min and max
python versions supported).

Also:
- changes tests with pytest.skip() to pass silently rather than skip
loudly if test not relevant to calendar.
- Removes following redundant errors:
  - `ScheduleFunctionWithoutCalendar`
  - `ScheduleFunctionInvalidCalendar`

Bumps [actions/cache](https://github.com/actions/cache) from 3.0.3 to 3.0.4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v3.0.3...v3.0.4)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Selective linting of exchange_calendar.py (using mypy and pylint).

Also, adds a mypy config section to setup.cfg.

Changes default calendar side to "left" for all calendars (from "right"
for 24h calendars and "both" for all others).

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 3 to 4.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v3...v4)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Updates README and tutorials for v4.0.

Also:
- adds `changes_renamed.md`.
- renames parameters of `minutes_in_range`.

Updates workflows:
- to accommodate changes to requirements files.
- on main workflow moves caching of dependencies to setup-python action.

Removes from etc:
- `requirements.in`
- `requirements_dev.in`
- `requirements_locked.txt`
- `requirements_locked_old.txt`

Adds following files generated from pip-compile looking at setup.cfg:
- `requirements.txt`
- `requirements_dev.txt`

Adds new `is_open_at_time` calendar method, adds tests and adds
example to calendar_methods.ipynb

Also
- corrects `minutes.ipynb` text that identifies which session break
bounds are considered as trading minutes for a given side.

Also updates README link to anticipated 4.0 disucssion address.