sqlstore: add support for checking if error is constraint validation error

pkg/services/sqlstore/migrator/postgres_dialect.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"github.com/go-xorm/xorm"
+	"github.com/lib/pq"
 )
 
 type Postgres struct {
@@ -136,3 +137,13 @@ func (db *Postgres) CleanDB() error {
 
 	return nil
 }
+
+func (db *Postgres) IsUniqueConstraintViolation(err error) bool {
+	if driverErr, ok := err.(*pq.Error); ok {
+		if driverErr.Code == "23505" {
+			return true
+		}
+	}
+
+	return false
+}