Ensure case insensitive search on postgres (#927)

Reviewed-on: https://kolaente.dev/vikunja/api/pulls/927
Co-authored-by: konrad <konrad@kola-entertainments.de>
Co-committed-by: konrad <konrad@kola-entertainments.de>

pkg/db/helpers.go

@@ -0,0 +1,35 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-2021 Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public Licensee as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public Licensee for more details.
+//
+// You should have received a copy of the GNU Affero General Public Licensee
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package db
+
+import (
+	"xorm.io/builder"
+	"xorm.io/xorm/schemas"
+)
+
+// ILIKE returns an ILIKE query on postgres and a LIKE query on all other platforms.
+// Postgres' is case sensitive by default.
+// To work around this, we're using ILIKE as opposed to normal LIKE statements.
+// ILIKE is preferred over LOWER(text) LIKE for performance reasons.
+// See https://stackoverflow.com/q/7005302/10924593
+func ILIKE(column, search string) builder.Cond {
+	if Type() == schemas.POSTGRES {
+		return builder.Expr(column+" ILIKE ?", "%"+search+"%")
+	}
+
+	return &builder.Like{column, "%" + search + "%"}
+}