Add support for named time zones in thin mode

Fetching timestamp with time zone raises error ORA-01805: possible error in date/time operation instead of returning datetime with time zone information.

1. What versions are you using?

   • database version: Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production
   • platform.python_version: 3.9.9
   • oracledb.__version__: 1.0.1

2. Is it an error or a hang or a crash? Error

3. What error(s) or behavior you are seeing?

Error oracledb.exceptions.DatabaseError: ORA-01805: possible error in date/time operation is raised when trying to use at time zone in SQL . Below is a sample code to reproduce the problem.

5. Does your application call init_oracle_client()? Yes, uses Thick mode.

6. Include a runnable Python script that shows the problem.

import oracledb
from oracledb.thick_impl import init_oracle_client


def f(sql):
    with oracledb.connect(user='hr', password='password', dsn='127.0.0.1:1511/xe') as connection:
        with connection.cursor() as cursor:
            query = cursor.execute(sql)
            row = query.fetchone()
            print(row[0].time())


init_oracle_client()

# this works because returns datetime without time zone
f("select systimestamp from dual")

# this raises error ORA-01805
f("select systimestamp at time zone 'America/Montreal' as d from dual")


# this is manual walkaround but datetime is still missing time zone information
f("select cast(systimestamp at time zone 'America/Montreal' as timestamp) as d from dual")

The above is an example using systimestamp but similar error can be achieved by crating table with column type timestamp with time zone

create table tz_table
(
	tz_timestamp TIMESTAMP(6) WITH TIME ZONE not null
);

insert into tz_table values ( TIMESTAMP '2022-06-16 08:00:00 US/Central');

Start with the runnable Python script in the issue and compare the failing named-time-zone query with the working timestamp queries in the stated Oracle 11g and driver setup. Done means fetching a timestamp with a named time zone returns datetime values that preserve time-zone information, including for the TIMESTAMP WITH TIME ZONE table example.