Asynch

- Add more validation rules in the `parse_dsn` function. By stankudrow in 113
- Reconsider the API of the `Connection`, `Cursor` and `Pool` classes and deprecate outdated methods or properties. Define the DB-API v2.0 compliant exception hierarchy. Update project dependencies and metadata. By stankudrow in 111.
- Fix infinite iteration case when a cursor object is put in the `async for` loop (the discussion 100 by KuzenkovAG). By stankudrow in 112.
- Fix pool connection management (the discussion 108 by DFilyushin) by stankudrow in 109:

- add the asynchronous context manager support to the `Pool` class with the pool "startup()" as `__aenter__` and "shutdown()" as `__aexit__` methods;
- enrich the `Pool` class with the "connection()" method returning an asynchronous context manager responsible for acquiring connections from a pool object and releasing them back into the pool;
- refactor the `Connection` and `Pool` classes.
- Add the asynchronous context manager support to the `Connection` class. By stankudrow in 107.
- Make Python3.9 the minimum supported version. Update the project dependencies, metadata, tests. By stankudrow in 106.

- Reset connection state. By boolka in 101.
- Add lazy date_lut, similar to clickhouse-driver. By DaniilAnichin in 99.
- Correct check life connection (71). By gnomeby in 98.
- Use maxsize for pool connections (68). By gnomeby in 97.
- Add Date32 column (95). By cortelf in 96.
- Eliminate `IndexError` cases from the `BufferedReader` class methods when reading from an empty buffer. By stankudrow in 94.
- Fix a bytearray index out of range error while reading a string. By pufit in 90.
- Make a connection be closed for `ExecuteContext` manager class. By KPull in 82.
- Add connection validity check in `acquire` method. By lxneng in 81.

- Support json column. (73)
- Fix connection with `secure=True` and `verify=False`.
- Fix compression.
- Fix exception `Cannot set verify_mode to CERT_NONE when check_hostname is enabled`.

- Add `Int128Column`, `Int256Column`, `UInt128Column`, `UInt256Column`, `Decimal256Column`. (57)
- Add Geo type support. (56)
- Add decimals in map support. (55)
- Add `NestedColumn`. (54)
- Add execution_options support. (53)
- Fix `IPv6Column`. (52)
- Fix execution context exception handling. (51)
- Fix stream_mode. (44)
- Fix `SimpleAggregateFunction` for nested. (41)

- Fix ping message for unstable network. (48)