Changes:
[#24] Use Spring Boot 2.3's GA Version
[#25] Custom adapters converting between JOOQ and R2DBC types
[#27] Support org.jooq.JSON with r2dbc-mysql
[#26] Support org.jooq.JSON and org.jooq.JSONB with r2dbc-postgresql
[#10] Run unit tests on all supported databases automatically
