Add String functions(concat)

[waahhh]

Motivation

• Support for String functions(concat)

Modifications

• Add JpqlConcat, JpqlConcatSerializer, dsl for concat function with tests

Commit Convention Rule

• Please commit your modification based by conventional commit:

Commit type	Description
feat	New Feature
fix	Fix bug
docs	Documentation only changed
ci	Change CI configuration
refactor	Not a bug fix or add feature, just refactoring code
test	Add Test case or fix wrong test case
style	Only change the code style(ex. white-space, formatting)
chore	It refers to minor tasks such as library version upgrade, typo correction, etc.

• If you want to add some more commit type please describe it on the Pull Request

Result

• Please describe the result after this PR is merged.

Closes

• #{issue number} (If this PR resolves an issue.)

[shouwn]

The String parameter should probably be nullable. When I tested it, both eclipselink and hibernate returned a blank character if null was passed in.

Users can take advantage of this functionality, so I don't think we should prevent it.

---

String 파라미터는 nullable이여야 할 것 같아요. 테스트 해보니 eclipselink 및 hibernate 모두 null이면 공백 문자를 반환해주었습니다.

사용자가 이 기능을 활용할 수 있기 때문에 저희가 막으면 안 될 것 같아요.

[waahhh]

String 파라미터는 nullable이여야 할 것 같아요. 테스트 해보니 eclipselink 및 hibernate 모두 null이면 공백 문자를 반환해주었습니다.

사용자가 이 기능을 활용할 수 있기 때문에 저희가 막으면 안 될 것 같아요.

그럼 말씀하신 케이스 고려해서 아래처럼 default value는 없이 변경하겠습니다.

    fun concat(
        value1: String?,
        value2: String?,
        vararg others: String?,
    ): Expression<String> {
        return Expressions.concat(
            Expressions.value(value1),
            Expressions.value(value2),
            others.map { Expressions.value(it) },
        )
    }

[shouwn]

넵! 감사합니다. ❤️

[waahhh]

@shouwn
리뷰 반영했습니다!