Add support for attaching volumette snapshots to workspaces

Summary:
Add server support for storing and retrieving workspaces with volumette snapshots attached to them.

Note that there isn't yet a way to use this from the Hargow CLI. We should wait for this to be fully deployed before adding client/worker support.

Reviewed By: mbassale

Differential Revision: D60269729

fbshipit-source-id: 0c235ae2c26b9ebe993982452e26a3bf9446f320

shed/sql/common/mysql.rs

@@ -72,6 +72,12 @@ pub trait AsSql {
     fn as_sql(&self, no_backslash_escape: bool) -> String;
 }
 
+impl AsSql for MySqlQuery {
+    fn as_sql(&self, _no_backslash_escape: bool) -> String {
+        self.query.clone()
+    }
+}
+
 impl<T: mysql_async::prelude::ToValue> AsSql for T {
     fn as_sql(&self, no_backslash_escape: bool) -> String {
         mysql_async::prelude::ToValue::to_value(self).as_sql(no_backslash_escape)