Feature: Generate fluent continuations to Asserts on properties

We would like to write something like:

@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<OtherClass> otherwise.

まず、プロパティアサーションを作成するジェネレーターコードを特定し、既存の ListAssert.singleElement() の動作を確認します。生成時およびフォールバック時の ObjectAssert の戻り値型をどのように選択すべきかを確認し、その後 SomeClass/OtherClass の例に対するカバレッジを追加します。