expire old SKPI hashes

src/sql.rs

@@ -874,6 +874,17 @@ pub async fn housekeeping(context: &Context) -> Result<()> {
         .log_err(context)
         .ok();
 
+    context
+        .sql
+        .execute(
+            "DELETE FROM tls_spki WHERE ? > timestamp + ?",
+            (time(), 30 * 24 * 60 * 60),
+        )
+        .await
+        .context("Failed to prune SPKI store")
+        .log_err(context)
+        .ok();
+
     // Cleanup `imap` and `imap_sync` entries for deleted transports.
     //
     // Transports may be deleted directly or via sync messages,