Replace tenant UUID by gen_random_uuid() in pg migration.

This should have been part of 5fd57de6ce7e5682a6b8e908acd28510cd4ba550.

chirpstack/migrations_postgres/00000000000000_initial/up.sql

@@ -63,7 +63,7 @@ insert into "tenant" (
     max_gateway_count,
     private_gateways
 ) values (
-    '52f14cd4-c6f1-4fbd-8f87-4025e1d49242',
+    gen_random_uuid(),
     now(),
     now(),
     'ChirpStack',

chirpstack/src/storage/tenant.rs

@@ -357,10 +357,19 @@ pub mod test {
     async fn test_tenant() {
         let _guard = test::prepare().await;
 
-        // delete default tenant
-        delete(&Uuid::from_str("52f14cd4-c6f1-4fbd-8f87-4025e1d49242").unwrap())
-            .await
-            .unwrap();
+        // delete existing tenants.
+        let tenants = list(
+            10,
+            0,
+            &Filters {
+                ..Default::default()
+            },
+        )
+        .await
+        .unwrap();
+        for t in &tenants {
+            delete(&t.id).await.unwrap();
+        }
 
         let mut t = create_tenant().await;