[Query] Support SPARQL XPath REGEX flags (x, q, s, m, i) and pattern matching #592

Summary

Implement full SPARQL 1.1 / XPath fn:matches flag support and pattern syntax compatibility for the REGEX built-in function.

Target Branch

• feature/corese-next

Specification & Semantics

According to W3C SPARQL 1.1 Query (§17.4.3.14 REGEX) invoking XPath fn:matches:

• Flag i: case-insensitive matching.
• Flag s: dot-all mode (. matches newline characters).
• Flag m: multiline mode (^ and $ match start/end of lines).
• Flag x: extended whitespace and comments (whitespace within pattern is ignored, # marks comments until end of line).
• Flag q: quote mode (pattern characters are treated literally without regex escaping).
• Character classes and bracket expressions [] must conform to standard XML Schema / XPath regular expressions.

Technical Context & Implementation Notes

1. Flag translation:

• In NativeExpressionEvaluator.java, map XPath flags to java.util.regex.Pattern flags:
  • i -> Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE
  • s -> Pattern.DOTALL
  • m -> Pattern.MULTILINE
  • x -> Pattern.COMMENTS
  • q -> Pattern.LITERAL

2. Compatibility handling:

• Combinations such as iq or x with bracket expressions must evaluate properly against target literals.

Targeted W3C SPARQL 1.0 / 1.1 Test Cases

• regex-query-003
• regex-query-004
• REGEX with [] expression
• REGEX with the ignore spacing (x) option
• REGEX with the ignore spacing (x) option with class expression
• REGEX with the q option
• REGEX with the iq option

Verification

• Unit tests (corese-core):
  ./gradlew test --tests "fr.inria.corese.core.next.query.impl.sparql.bridge.NativeExpressionEvaluatorTest"
• W3C conformance (corese-w3c):
  ./gradlew test --tests "fr.inria.corese.w3c.sparql10.Sparql10DynamicTest"

Acceptance Criteria

[ ] All standard XPath flags (i, s, m, x, q) are recognized and properly converted to Java regex flags.
[ ] Flag x correctly ignores whitespaces and ignores comments starting with #.
[ ] Flag q treats the pattern as a literal string.
[ ] The 7 targeted W3C SPARQL 1.0 regex tests pass.
[ ] 0 SonarLint issues and cognitive complexity < 15.