Django 4.2 introduced table comments. These are comments that are part

of the table schema, describing a table, and are supported in MySQL 8+

and Postgres 12+ (the minimum versions that Django 4.2 supports), but

not SQLite.
This supports signature storage of table comments and evolutions via

ChangeMeta.
This functionality is required for Django 4.2 support, as this is

introspected on our mock models, and we don't want to risk storing empty

values or misleading the backend. Fortunately, as we can piggy-back on

SchemaEditor, support is easy to add and maintain going forward.

Ran unit tests for SQLite, Postgres, and MySQL on a range of database

versions on Python 3.11 and 3.12, Django 3.2-4.2, which should provide

sufficient coverage for this feature.