[BUG][Java] BeanValidation patterns dont match across newlines

Bug Report Checklist

• Have you provided a minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

actual @Pattern(regexp = ".")
expected @Pattern(regexp = ".", flags = { Pattern.Flag.DOTALL })

openapi-generator version

latest (code check)

OpenAPI declaration file content or url

type: string
pattern: .*

Generation Details

Steps to reproduce

• use the above for a generation
• this will generate a Pattern(".*)
• if you then send a validated property with new lines against it , it will not match

Related issues/PRs

Suggest a fix

add DOT_ALL either by default or with a config flag (due to potential breaking change)
https://github.com/OpenAPITools/openapi-generator/blob/6da343a8ad1176875f27e7a4465164646574dc3d/modules/openapi-generator/src/main/resources/JavaSpring/beanValidationCore.mustache

Start with modules/openapi-generator/src/main/resources/JavaSpring/beanValidationCore.mustache and reproduce the issue using the provided OpenAPI declaration with a Java Spring generation. Compare the generated @Pattern annotation with the expected DOTALL form. Done means multiline values match the generated Bean Validation pattern, with the breaking-change/config-flag choice addressed.