Unable to create table with ALPHANUM column

**Describe the bug** Creating a table with a column of type ALPHANUM fails with `AttributeError`. **To Reproduce** ```python from sqlalchemy import MetaData, Table, Column from sqlalchemy_hana.types import ALPHANUM engine = None # Engine pointed at SAP HANA meta = MetaData() mytab = Table("mytab", meta, Column("mycol", ALPHANUM(10)), schema="my_schema") meta.create_all(engine) # AttributeError: 'HANATypeCompiler' object has no attribute 'visit_ALPHANUM' ``` **Expected behavior** The table should be created and no error should be raised. **Versions (please complete the following information):** - `sqlalchemy` 1.4.39 - `sqlalchemy-hana` 1.2.0 - `python` 3.9 - `SAP HANA version and edition (cloud/on-prem)` 2.00.073.00.1695288802 (on-prem)