Not accepting str as value for interval/date columns

• asyncpg version: 0.29.0
• PostgreSQL version: 15.7
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: local
• Python version: 3.11
• Platform: Windows
• 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
• Can the issue be reproduced under both asyncio and
  uvloop?: yes

I am using asyncpg as the driver for SQLAlchemy.

class Table(Base):
    __tablename__ = 'table'
    interval: Mapped[timedelta]

session.add(Table(interval='1 min'))

With the above code, it throws this error:
sqlalchemy.exc.DBAPIError: (sqlalchemy.dialects.postgresql.asyncpg.Error) <class 'asyncpg.exceptions.DataError'>: invalid input for query argument $9: '1 min' ('str' object has no attribute 'days')

However, Postgresql accepts '1 min' as a value to an interval column. Why is asyncpg forbidding str even though Postgresql accepts it in this case?

Start by reproducing the SQLAlchemy example with the stated PostgreSQL 15.7 and Python 3.11 setup, then trace asyncpg parameter handling for interval and date values. Compare string inputs with PostgreSQL's accepted interval syntax and add regression coverage that captures the intended result.