Entity_.__ALL_RELATIONS like __ALL_PROPERTIES

Hi,

it would be great if generated entity class had access to array of RelationInfo like it has access to all properties.
Right now eager loading relations requires

1. explicit list of all relations and QueryBuilder.eager
   or
2. hard reflection loop calling getTarget()

Explicit list __ALL_RELATIONS would ease up creating algorithms like eager loading.

What do you think?

首先检查生成的实体类如何暴露 __ALL_PROPERTIES，然后跟踪 RelationInfo 和 QueryBuilder.eager 在所述 eager-loading 情况下的使用。完成的标准是：生成的实体提供一个类似的 __ALL_RELATIONS 数组，以支持关系发现算法，并为生成的 API 提供覆盖。