@spec build_attribute(atom(), atom(), keyword(), [map()] | nil) :: map()

Builds an attribute map from DSL options.

The key presence varies by type to match existing schema behavior:

• string: includes caseExact and uniqueness
• boolean: no caseExact, uniqueness optional (only if explicitly provided)
• complex: includes subAttributes, mutability, returned, uniqueness
• reference: includes referenceTypes, caseExact, uniqueness

@spec build_schema(String.t(), String.t(), String.t(), [map()]) :: map()

Builds the complete schema map from DSL-collected data.

@spec build_sub_attribute(atom() | String.t(), atom(), keyword()) :: map()

Builds a sub-attribute map (used inside complex attributes).