backend-common: clarify DB connection error

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/fair-points-grin.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-common': patch
+---
+
+Provide a more clear error message when database connection fails.

packages/backend-common/src/database/SingleConnection.ts

@@ -77,6 +77,12 @@ export class SingleConnectionDatabaseManager {
 
   private async ensureDatabase(database: string) {
     const config = this.config;
-    await ensureDatabaseExists(config, database);
+    try {
+      await ensureDatabaseExists(config, database);
+    } catch (error) {
+      throw new Error(
+        `Failed to connect to the database to make sure that '${database}' exists, ${error}`,
+      );
+    }
   }
 }