feat(NIP-40): postgres support for event expiration

src/repo/postgres_migration.rs

@@ -35,6 +35,7 @@ pub async fn run_migrations(db: &PostgresPool) -> crate::error::Result<usize> {
         m002::rebuild_tags(db).await?;
     }
     run_migration(m003::migration(), db).await;
+    run_migration(m004::migration(), db).await;
     Ok(current_version(db).await as usize)
 }
 
@@ -256,3 +257,23 @@ ALTER TABLE tag ADD CONSTRAINT unique_constraint_name UNIQUE (event_id, "name",
         }
     }
 }
+
+mod m004 {
+    use crate::repo::postgres_migration::{Migration, SimpleSqlMigration};
+
+    pub const VERSION: i64 = 4;
+
+    pub fn migration() -> impl Migration {
+        SimpleSqlMigration {
+            serial_number: VERSION,
+            sql: vec![
+                r#"
+-- Add expiration time for events
+ALTER TABLE event ADD COLUMN expires_at timestamp(0) with time zone;
+-- Index expiration time
+CREATE INDEX event_expires_at_idx ON "event" (expires_at);
+        "#,
+            ],
+        }
+    }
+}