feat(postgres): Added support for PostgreSQL OID type conversion (as u32)

[alexander-beedie]

Minor addition of support for the oid PostgreSQL identifier type, so it's a little easier to interact with system tables; oid is a u32 type, and can be directly read as such.

Ref: PostgreSQL OID type details.

Example

Loading some data from the pg_class system table:

import connectorx as cx

cx.read_sql(
    conn="postgresql://<user>:<pass>@<host>:<port>/<db>",
    query="""
        SELECT oid, relname 
        FROM pg_class
        WHERE relkind = 't'
    """,
    return_type="polars",
)

Before:

# PanicException: not implemented: oid

After:

# shape: (88, 2)
# ┌───────────┬────────────────────┐
# │ oid       ┆ relname            │
# │ ---       ┆ ---                │
# │ u32       ┆ str                │
# ╞═══════════╪════════════════════╡
# │ 75665     ┆ pg_toast_75661     │
# │ 75676     ┆ pg_toast_75672     │
# │ 337455076 ┆ pg_toast_337455072 │
# │ …         ┆ …                  │
# │ 3772379   ┆ pg_toast_3772376   │
# │ 3772397   ┆ pg_toast_3772393   │
# │ 4066652   ┆ pg_toast_4066648   │
# └───────────┴────────────────────┘

[wangxiaoying]

Thanks @alexander-beedie !