NestedJoin is not implemented

[wangxiaoying]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

import polars as pl

df1 = pl.DataFrame(
        {
            "id": [1, 2, 3, 4],
            "name": ["a", "b", "c", "d"]
        }
    )
df2 = pl.DataFrame(
        {
            "id": [1, 2, 3, 5],
            "type": ["ta", "tb", "tc", "td"]
        }
    )
df3 = pl.DataFrame(
        {
            "id": [1, 2, 5, 6],
            "class": ["ca", "cb", "cc", "cd"]
        }
    )

ctx = pl.SQLContext()
ctx.register("df1", df1)
ctx.register("df2", df2)
ctx.register("df3", df3)

lf = ctx.execute("select df1.id, df1.name, df2.type, df3.class from df1 inner join (df2 inner join df3 on df2.id=df3.id) on df1.id=df2.id")

Log output

polars.exceptions.SQLInterfaceError: not yet implemented: (df2 JOIN df3 ON df2.id = df3.id)

Issue description

NestedJoin is not implemented

Expected behavior

Query executed correctly, as the same query can be executed on postgres. (Enabling this can also use nested join to control the join order manually)

Installed versions

--------Version info---------
Polars:               1.3.0
Index type:           UInt32
Platform:             macOS-13.2.1-arm64-arm-64bit
Python:               3.11.8 (main, Feb 22 2024, 21:34:36) [Clang 14.0.0 (clang-1400.0.29.202)]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          <not installed>
connectorx:           0.3.3
deltalake:            <not installed>
fastexcel:            <not installed>
fsspec:               <not installed>
gevent:               <not installed>
great_tables:         <not installed>
hvplot:               <not installed>
matplotlib:           3.9.1
nest_asyncio:         1.6.0
numpy:                1.26.4
openpyxl:             <not installed>
pandas:               2.2.2
pyarrow:              16.1.0
pydantic:             <not installed>
pyiceberg:            <not installed>
sqlalchemy:           2.0.31
torch:                <not installed>
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>