Validator for the restricted JSON Schema subset allowed in elicitation requests.

Per the MCP 2025-06-18 specification, an elicitation/create requestedSchema must be a flat object whose properties are all primitives. This module validates both the schema map itself (validate/1) and content payloads against a previously validated schema (validate_content/2).

Permitted property schemas:

• string with optional minLength, maxLength, format (one of "email", "uri", "date", "date-time")
• string enum with enum and optional matching enumNames
• number / integer with optional minimum, maximum
• boolean with optional default