Rollback large explicit transactions in background.

Client usually does not care about a transaction after rollback

cdstar-rest/src/main/java/de/gwdg/cdstar/rest/v3/TransactionEndpoint.java

@@ -2,9 +2,9 @@ package de.gwdg.cdstar.rest.v3;
 
 import java.time.Duration;
 
+import de.gwdg.cdstar.rest.api.RestBlueprint;
 import de.gwdg.cdstar.rest.api.RestConfig;
 import de.gwdg.cdstar.rest.api.RestContext;
-import de.gwdg.cdstar.rest.api.RestBlueprint;
 import de.gwdg.cdstar.rest.utils.QueryHelper;
 import de.gwdg.cdstar.rest.utils.SessionHelper;
 import de.gwdg.cdstar.rest.v3.async.ModelHelper;
@@ -64,7 +64,8 @@ public class TransactionEndpoint implements RestBlueprint {
 	}
 
 	public Void handleDelete(RestContext ctx) throws Exception {
-		getTxOr404(ctx).rollback();
+		CDStarSession tx = getTxOr404(ctx);
+		ctx.runInPool(tx::rollback); // Close in background
 		ctx.status(204);
 		return null;
 	}
@@ -75,7 +76,7 @@ public class TransactionEndpoint implements RestBlueprint {
 			throw new ErrorResponse(404, "TransactonNotFound", "No transaction specified");
 
 		final CDStarSession session = ctx.getService(CDStarRuntime.class).resumeSession(txid);
-		if (session == null)
+		if (session == null || session.isExpired())
 			throw new ErrorResponse(404, "TransactonNotFound", "Unknown or expired transaction").detail("transaction",
 				txid);
 		return session;