category
Declares the problem category. It offers a hierarchical categorization with arbitrary details. Clients must declare a main category string. Freeform with the following conventions and limitations. Subcategories can be optionally specified with arbitrary details. The same conventions and limitations apply. When a problem is created (with BuildableProblemBuilder.build()) the category can be obtained with Problem. The `ProblemCategory` then represents a local category with some namespace, distinguishing built-in and third-party categories. Example: category("validation", "missing-input")
Return
the builder for the next required property
Parameters
category
the type name
details
the type details