Consider custom conversion in EntityRowMapper and MappingR2dbcConverter

[asavov]

spring-data-r2dbc/src/main/java/org/springframework/data/r2dbc/function/convert/EntityRowMapper.java

Line 72 in 2dfb1ff

if (property.isMap()) {

Reading of Map entity property is intentionally blocked by above line.

How about allowing it and then delegate to the client's custom DBStoredValue-To-Map converter. Similar to:

    static class Config extends AbstractR2dbcConfiguration {

        @Override @Bean public R2dbcCustomConversions r2dbcCustomConversions() {
            ...
            return new R2dbcCustomConversions(
                    storeConversions,
                    Arrays.asList(new JsonStringToMapConverter()));
        }

        class JsonStringToMapConverter implements Converter<String, Map<String, Object>> {
             ...
        }

[asavov]

Seems kind of related to #39
Still if (property.isMap()) throw new UnsupportedOperationException(); needs special attention which is orthogonal to #39

[mp911de]

The mentioned guard above will be removed with the implementation of #39.

[mp911de]

That's in place now.