fix(dbapi2): preserve XRayTracedConn wrapper in connection context manager

[reginaldalfret]

Fixes #490

Problem

When using a database connection wrapped by \XRayTracedConn\ within a context manager (\with conn as c:), \wrapt.ObjectProxy\ forwards _enter_\ to the underlying database connection. Since DBAPI and driver \Connection.enter()\ returns \self\ (the underlying connection object), \c\ ends up referencing the unwrapped connection rather than \XRayTracedConn. Consequently, subsequent \c.cursor()\ calls return raw cursors, and SQL queries executed inside the context manager are not traced by X-Ray.

Root Cause

\XRayTracedCursor\ already implements _enter_\ to return \self\ when _wrapped_.enter()\ returns the underlying object, but \XRayTracedConn\ was missing the corresponding _enter_\ implementation.

Solution

Implement _enter_\ on \XRayTracedConn\ matching the existing pattern in \XRayTracedCursor:
\\python
def enter(self):
value = self.wrapped.enter()
if value is not self.wrapped:
return value
return self
\\

Validation

• Added regression test \ est_connection_context_manager\ in \ ests/ext/sqlite3/test_sqlite3.py\ demonstrating that \with db as conn:\ preserves the traced connection wrapper and correctly records SQL subsegments.
• Confirmed test fails without the fix (\IndexError: list index out of range\ due to missing subsegments) and passes cleanly with the fix.
• Ran all existing SQLite3 and recorder tests (39 passed).