Fix JSONB parameter binding to prevent psycopg2 dict adaptation errors

[Copilot]

Fix JSONB parameter binding to prevent psycopg2 dict adaptation errors

Description

PostgreSQL drivers cannot automatically adapt Python dict and List[dict] types to JSONB when passed as raw parameters, causing psycopg2.ProgrammingError: can't adapt type 'dict'.

Changes

• Type binding for single messages: Use bindparam("message", type_=JSONB) instead of SQL CAST(:message AS jsonb)
• Type binding for batch messages: Use bindparam("messages", type_=ARRAY(JSONB)) instead of SQL CAST(:messages AS jsonb[])
• Statement execution: Return pre-bound text objects from _get_send_statement and _get_send_batch_statement methods

Example

from sqlalchemy import text, bindparam
from sqlalchemy.dialects.postgresql import JSONB, ARRAY

# Before: SQL-level casting (fails with dict adaptation)
stmt = text("SELECT pgmq.send(:queue, CAST(:message AS jsonb), :delay)")

# After: SQLAlchemy type binding (proper adaptation)
stmt = text("SELECT pgmq.send(:queue, :message, :delay)").bindparams(
    bindparam("message", type_=JSONB)
)

This ensures correct type adaptation across all PostgreSQL drivers (psycopg2, psycopg, pg8000, asyncpg).

Status

• In progress
• Ready for review
• Done

Checklist

• Read the Contributing Guide
• Passes tests
• Linted ( we use pre-commit with ruff )
• Updated documentation

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