Add new error for "Violation Check Constraint"

[anilsenay]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

Add new error for "Check Constraint Violation"

User Case Description

I added a check constraint in my table in PostgreSQL such as:
CONSTRAINT path_check CHECK (path ~ '^/[a-zA-Z0-9\-]+$')

When an error occurs when I try to add a new row to the table, I want to be sure that it is a rule violation error or another type of error.

if errors.Is(result.Error, gorm.ErrCheckConstraintViolated) {
  // handle check constraint violation error
}

Pull request for go-gorm/postgres: go-gorm/postgres#271