When `permissions_validity_in_ms` is set to 0, executing a prepared statement under authentication crashes with:
```
Assertion `caching_enabled()' failed.
at utils/loading_cache.hh:319
in authorized_prepared_statements_cache::insert
```
`loading_cache::get_ptr()` asserts when caching is disabled (expiry == 0), but `authorized_prepared_statements_cache::insert()` was using it purely for its side effect of populating the cache, which is meaningless when caching is off.
Add a new `loading_cache::insert(k, load)` method that is a no-op when caching is disabled and otherwise forwards to `get_ptr()`. Switch `authorized_prepared_statements_cache::insert()` to use it. This
completes the disabled-mode safety contract of the cache for the write side, mirroring the fallback that `get()` already provides for the read side.
Includes a regression test in `test/boost/loading_cache_test.cc` plus a positive test for the new `insert()` overload.
Fixes SCYLLADB-1699
The crash is introduced a long time ago. It is present on all the live versions, from 2025.1 onward. No client tickets, but it should be backported.
Closesscylladb/scylladb#29638
* github.com:scylladb/scylladb:
test: boost: regression test for loading_cache::insert with caching disabled
utils: loading_cache: add insert() that is a no-op when caching is disabled
(cherry picked from commit c00fee0316)
Closesscylladb/scylladb#29762
9e0c86b7fd