Add Native Sharing REST API (#1150)

* Initial draft - UNTESTED

* changes to Save() and Update()

* apply col filter and limit nanoid

* remove columns to not update

db/migration/20210601231734_update_share_fieldnames.go

@@ -0,0 +1,25 @@
+package migrations
+
+import (
+	"database/sql"
+
+	"github.com/pressly/goose"
+)
+
+func init() {
+	goose.AddMigration(upUpdateShareFieldNames, downUpdateShareFieldNames)
+}
+
+func upUpdateShareFieldNames(tx *sql.Tx) error {
+	_, err := tx.Exec(`
+alter table share rename column expires to expires_at;
+alter table share rename column created to created_at;
+alter table share rename column last_visited to last_visited_at;
+`)
+
+	return err
+}
+
+func downUpdateShareFieldNames(tx *sql.Tx) error {
+	return nil
+}