add ability to notify multiple tg subscribers about new messages in t…

…he configured mail inbox

src/main/resources/db/migration/V1_013__mail-forwarding-to-multiple-subscribers.sql

@@ -0,0 +1,17 @@
+create table mail_subscriber
+(
+    mail_configuration_id int8 not null,
+    tg_source_id          int8 not null
+);
+
+create unique index mail_subscriber_mail_configuration_id_tg_source_id
+    on mail_subscriber (mail_configuration_id, tg_source_id);
+
+update mail_subscriber
+set mail_configuration_id = mc.id,
+    tg_source_id          = mc.tg_source_id
+from mail_configuration mc
+where mc.tg_source_id is not null;
+
+alter table mail_configuration
+    drop column tg_source_id;