Connect DSN doesn't handle @ in username

[rudigiesler]

• asyncpg version: 0.20.1
• PostgreSQL version: 9.6
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: Azure PostgreSQL. It is reproducible with a local install.
• Python version: 3.7.7
• Platform: Docker/Debian, locally OSX
• Do you use pgbouncer?: No
• Did you install asyncpg with pip?: Yes
• If you built asyncpg locally, which version of Cython did you use?: N/A, installed from wheel.
• Can the issue be reproduced under both asyncio and
  uvloop?: Yes

Azure managed databases have credentials as follows:
url: instance-name.privatelink.postgres.database.azure.com
database: db-name
username: db-name@instance-name
password: password

Combining that into a DSN, we get something like:
postgres://db-name@instance-name:password@instance-name.privatelink.postgres.database.azure.com:5432/db-name

But the utility to interpret the DSN makes a mistake when trying to interpret a DSN of this shape:

  File "/turn-rasa-connector/turn_rasa_connector/turn.py", line 163, in get_postgresql_pool
    self._postgresql_pool = await asyncpg.create_pool(self.postgresql_url)
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/pool.py", line 398, in _async__init__
    await self._initialize()
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/pool.py", line 426, in _initialize
    await first_ch.connect()
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/pool.py", line 125, in connect
    self._con = await self._pool._get_new_connection()
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/pool.py", line 472, in _get_new_connection
    **self._connect_kwargs)
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/connection.py", line 1677, in connect
    max_cacheable_statement_size=max_cacheable_statement_size)
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/connect_utils.py", line 645, in _connect
    addrs, params, config = _parse_connect_arguments(timeout=timeout, **kwargs)
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/connect_utils.py", line 496, in _parse_connect_arguments
    server_settings=server_settings)
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/connect_utils.py", line 236, in _parse_connect_dsn_and_args
    host, port = _parse_hostlist(dsn_hostspec, port, unquote=True)
  File "/opt/venv/lib/python3.7/site-packages/asyncpg/connect_utils.py", line 196, in _parse_hostlist
    hostlist_ports.append(int(hostspec_port))
ValueError: invalid literal for int() with base 10: 'password@instance-name.privatelink.postgres.database.azure.com:5432'

It seems like it is taking the first @ symbol when splitting between the instance name and credentials, instead of the last @ symbol.

This also happens locally when creating a user that has an @ symbol in the username.

[rudigiesler]

I see this was solved in #472 , and percent encoding should be used instead. Closing.