Add has_def column field which is calculated by searching default val…

…ue or generated as identity

Add default column field

Migrate to go1.18 & go-pg v10 & fix tests

Fix zero dimensions in arrays

Add json tag feature (idea: @orange-jacky)

Fix table name for gopg v10

Fix #40 Add rel tag to has-one relations

Add schemas getter

Make CustomType public

Add custom types support