store: Add fields to store errors from pruning in prune_state

Author: lutter

store/postgres/migrations/2025-04-25-163121_prune_error/down.sql

@@ -0,0 +1,3 @@
+alter table subgraphs.prune_state
+  drop column errored_at,
+  drop column error;

store/postgres/migrations/2025-04-25-163121_prune_error/up.sql

@@ -0,0 +1,4 @@
+alter table subgraphs.prune_state
+  add column errored_at timestamptz,
+  add column error text,
+  add constraint error_ck check ((errored_at is null) = (error is null));

store/postgres/src/relational/prune.rs

@@ -534,6 +534,8 @@ mod status {
 
             started_at -> Timestamptz,
             finished_at -> Nullable<Timestamptz>,
+            errored_at -> Nullable<Timestamptz>,
+            error -> Nullable<Text>,
         }
     }
 
@@ -633,6 +635,9 @@ mod status {
 
         pub started_at: DateTime<Utc>,
         pub finished_at: Option<DateTime<Utc>>,
+
+        pub errored_at: Option<DateTime<Utc>>,
+        pub error: Option<String>,
     }
 
     /// Per-table information about the pruning run for a deployment