Handful of small improvements

Features

• add db connection event types (4862c7d)
• model_query_builder: add error.model for E_ROW_NOT_FOUND; (#1081) (334186f)
• preloader: add preloadOnce to preload a relationship only once (#1078) (fbfadbe)

What's Changed

• Add db connection event types by @adrianNEMO in #1074
• feat(preloader): add preloadOnce to preload a relationship only once by @zaosoula in #1078
• added decimalNumbers config to connection properties for compatibility to mysql by @siddiquipro in #1080
• feat(model_query_builder): add error.model for E_ROW_NOT_FOUND; by @radiumrasheed in #1081

New Contributors

• @adrianNEMO made their first contribution in #1074
• @radiumrasheed made their first contribution in #1081

Full Changelog: v21.5.1...v21.6.0