Feature: Generate fluent continuations to Asserts on properties

We would like to write something like:

```java
@Data
class SomeClass {
String id;
OtherClass someField;
}

@Data
class OtherClass {
String value;
}

@Test
void test() {
SomeClass someObject = ...;
assertThat(someObject)
.hasName("foo")
.someField()
.hasValue("abc")
}
```

That is particularly useful when working on POJO trees as, for example, generated when parsing JSON/YAML documents.
(Inspired by `ListAssert.singleElement()`.)

That is assuming, of course, that we generate the assertions for `SomeClass`.
The return type would be `OtherClassAssert` if we generate the assertions for _that_ class as well, of `ObjectAssert` otherwise.