fix(Cloud Databases): fix Unwrap return value for go 1.18 compat

Signed-off-by: Alex Hemard <alexhemard@gmail.com>

ibm/service/database/resource_ibm_database.go

@@ -83,14 +83,21 @@ func (e *databaseUserValidationError) Error() string {
 		if i > 0 {
 			b = append(b, '\n')
 		}
-		b = append(b, err.Error()...)
+		if err != nil {
+			b = append(b, err.Error()...)
+		}
 	}
 
 	return fmt.Sprintf("database user (%s) validation error:\n%s", e.user.Username, string(b))
 }
 
-func (e *databaseUserValidationError) Unwrap() []error {
-	return e.errs
+func (e *databaseUserValidationError) Unwrap() error {
+	if e == nil || len(e.errs) == 0 {
+		return nil
+	}
+
+	// only return the first
+	return e.errs[0]
 }
 
 type userChange struct {