PagedModel.getMetadata method should not be annotated with @Nullable

[hashpyrit]

In the class org.springframework.data.web.PagedModel the getMetadata method is annotated with @nullable.

Based on how the code is written, with page being mandatory as part of the constructor, the getMetadata method should always return an object, never null.

This is causing issues with typescript generation where it's saying that the metadata is optional, when it's really not. It will always be present based on how the code is written.

Additionally, it seems odd to have a page without mandatory paging information.