asyncpg does not work with "sslmode" query param when called from SQLAlchemy

• asyncpg version: 0.22
• PostgreSQL version: 12.3
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: I use DigitalOcean and was able to also reproduce it locally
• Python version: 3.8.9
• Platform: Linux
• Do you use pgbouncer?: No
• Did you install asyncpg with pip?: Yes
• If you built asyncpg locally, which version of Cython did you use?: -
• Can the issue be reproduced under both asyncio and
  uvloop?: N/D

First, congratulation to the people of MagicStack for this great library.

When using DigitalOcean default environment DATABASE URL to set the database string on my app I got the following error:

  File "/usr/local/lib/python3.8/site-packages/sqlalchemy/pool/base.py", line 599, in __connect
    connection = pool._invoke_creator(self)
  File "/usr/local/lib/python3.8/site-packages/sqlalchemy/engine/create.py", line 578, in connect
    return dialect.connect(*cargs, **cparams)
  File "/usr/local/lib/python3.8/site-packages/sqlalchemy/engine/default.py", line 558, in connect
    return self.dbapi.connect(*cargs, **cparams)
  File "/usr/local/lib/python3.8/site-packages/sqlalchemy/dialects/postgresql/asyncpg.py", line 747, in connect
    await_only(self.asyncpg.connect(*arg, **kw)),
TypeError: connect() got an unexpected keyword argument 'sslmode'

In my app, since I use psycopg2 to do some "management tasks", I also need to do something like that:

if ssl_enabled and driver == "asyncpg":
    base_url += "?ssl=require"
elif ssl_enabled and driver == "psycopg2":
    base_url += "?sslmode=require"

Shouldn't asyncpg use the more standard sslmode= query param instead of the ssl=?

Beginne mit dem im Traceback gezeigten SQLAlchemy-PostgreSQL-asyncpg-Dialektpfad, insbesondere sqlalchemy/dialects/postgresql/asyncpg.py, und verfolge, wie die URL-Abfrageparameter asyncpg.connect erreichen. Reproduziere den Fehler mit sslmode=require und vergleiche ihn mit ssl=require. Als erledigt gilt die Aufgabe, wenn der vorgesehene Parameter über SQLAlchemy ohne den Fehler „unexpected keyword“ funktioniert und eine Abdeckung für den Fall mit der Verbindungs-URL vorhanden ist.