feat(entity): add cascade option support for entity relationships

[CharlesWong]

Feature: Cascade Entity Relationships

Adds support for cascade operations on JHipster entity relationships, as requested in #12844.

JDL Syntax

relationship ManyToOne {
  Order{customer} to Customer with cascade
}

Generated Code

@ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private Customer customer;

How It Works

The cascade keyword is added as a new relationship option token in the JDL grammar. When specified:

1. The JDL lexer tokenizes cascade as a CASCADE token
2. The parser accepts it in the relationshipOption rule alongside builtInEntity
3. The AST builder visitor maps it to the cascade option name
4. The JDL-to-JSON converter propagates it into relationship.options.cascade = true
5. The relationship.options are spread onto the relationship object (existing behavior)
6. The Jakarta Persistence EJS template emits the appropriate CascadeType on all relationship types

Supported Cascade Types

• with cascade — CascadeType.ALL (unary shorthand)

Supported Relationship Types

• @OneToMany — @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, ...)
• @ManyToOne — @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
• @ManyToMany — @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, ...)
• @OneToOne — @OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL, ...)

Files Changed

• lib/jdl/core/built-in-options/relationship-options.ts — adds CASCADE constant
• lib/jdl/core/parsing/lexer/lexer.ts — registers cascade token
• lib/jdl/core/parsing/jdl-parser.ts — accepts cascade in relationshipOption rule
• lib/jdl/core/parsing/jdl-ast-builder-visitor.ts — handles CASCADE token in visitor
• lib/jdl/converters/jdl-to-json/jdl-to-json-relationship-converter.ts — propagates cascade option
• generators/spring-boot/generators/data-relational/templates/.../_persistClass_.java.jhi.jakarta_persistence.ejs — emits CascadeType in JPA annotations

Closes #12844