Make it possible to run a custome SQL command from within a test

[benedeki]

Feature Description

Add (a) method(s) to DBTestSuite that will allow to execute a custom SQL code as part of the test.

(no need for parametrized queries support, at least yet)

Problem / Opportunity

Sometimes a database test needs to run a different SQL than just interaction with table or calling a function.

Acceptance Criteria

1. User of the library can run a custom SQL

Proposed Solution

Add methods:

• sql that returns a result set, similar to table query or function call
• ddl that returns no results
• (possible) dml, that allows to modify data, returning the rows modified
  • auto-adding RETURNING, if not present
  • possible to call with verification as table query, or without

Dependencies / Related

No response

Additional Context

No response