Add clause variant to findBy method

Latest 20.5.0 was missing some commits.
This release is published only as a patch since 20.5.0 was released a few minutes ago.

• feat(base_model): add clause variant to findBy method (#1020) 059c472
• fix(base_model): correct typing for findManyBy c22f019
• Merge pull request #1013 from MaximeMRF/feat-step-option-migrator 196c97c
• feat(Migrator): add step option 4012129

v20.4.0...v20.5.1