fix(c/driver/sqlite): support PRIMARY KEY constraint in GetObjects

[lidavidm]

Fixes #666.

[lidavidm]

TODO: Use the new helper from #769

[lidavidm]

Hmm, the new helper is a little too rigid for SQLite's purposes

[lidavidm]

Just needs a small bend to work!

[lidavidm]

Hmm, I just realized, why is this all in utils.c in the first place? Seems like it should go in adbc_validation_util.cc...

[WillAyd]

I think the ASAN problem is with the destructor - I think can push up a fix soon

[WillAyd]

I think should be resolved by #785

[WillAyd]

Hmm is this function receiving a nullptr? Seems a bit strange to call a GetByName function, pass it a NULL pointer for the name and expect a result back

[WillAyd]

Current implementation does allow for UB if constraint_name is NULL so makes sense to return early if that happens, though I think that should be on function entry and also just return NULL there instead of grabbing the first constraint?

[lidavidm]

Fair.

SQLite doesn't name its constraints so I wanted some way to just get any constraint.

[WillAyd]

Ah OK. In that case maybe you want to do something like this instead?

  struct AdbcGetObjectsTable* table =
      AdbcGetObjectsDataGetTableByName(*get_objects_data, quirks()->catalog().c_str(),
                                       quirks()->db_schema().c_str(), "adbc_pkey_test");
  if (table->n_table_constraints > 0) {
    struct AdbcGetObjectsConstraint *constraint = table->table_constraints[0];
    ...
  }

[WillAyd]

Alternately could add a AdbcGetObjectsDataGetConstraintByPosition function

[lidavidm]

Ah, nice. I'll update it tomorrow morning