Consider to add check for columns with type json

[mfvanek]

With json type it's possible to get an error
org.postgresql.util.PSQLException: ERROR: could not identify an equality operator for type json
in queries like
select distinct id, json_column from table_with_json;

We should avoid using json type.
Jsonb should be preferred instead

[mfvanek]

-- Finds columns of type 'json'. Use 'jsonb' instead.
select
    t.oid::regclass::text as table_name,
    col.attname::text as column_name,
    col.attnotnull as column_not_null
from pg_catalog.pg_class t
         join pg_catalog.pg_namespace nsp on nsp.oid = t.relnamespace
         join pg_catalog.pg_attribute col on (col.attrelid = t.oid)
where
        t.relkind = 'r' and
        col.attnum > 0 and /* to filter out system columns such as oid, ctid, xmin, xmax, etc.*/
        col.atttypid::regtype::text = 'json' and
        nsp.nspname = :schema_name_param::text
order by t.oid::regclass::text, col.attname::text;