Fix some Doctrine runtime exceptions

[stweil]

Doctrine ORM expects an entity class, not an interface. Doctrine cannot instantiate or query interfaces—only concrete classes.

The mapping in PluginManager.php only applies to dependency injection and factory-based object creation, not to Doctrine ORM DQL queries.

[stweil]

I only see the exceptions in the debugger, but according to the information which I found (partially with AI support) the previous code cannot work.

Note that there are more similar code locations which also might. need a fix.

[EreMaijala]

Doctrine can resolve the interfaces to the target classes using its ResolveTargetEntityListener that's initialized in module/VuFind/src/VuFind/Db/EntityManagerFactory.php. While it uses an exception internally to trigger the fallback loader, the exception won't be passed on if the interface gets resolved to an actual class.

If this was really a problem, VuFind's database functionality would not work at all. The interfaces are used everywhere.

There is a similar case of runtime exceptions happening for command-specific arguments in console utilities, and it's not a real problem either. While it can be argued that using exceptions for normal control flow is inappropriate, VuFind also does that internally e.g. to trigger an authentication request.

[demiankatz]

Please see the conversation thread on #2233 about this issue -- this is the way it is by design, and it does work correctly. I believe that we should probably close this PR without changes, but if you want to discuss the Doctrine implementation in more detail, please feel free to join a Community Call (there is one today at 13:00 GMT).

As @EreMaijala says, if we wanted to change our approach to DQL generation, we would have to make many more changes than the ones in this PR. But I do not think we want to change it, based on my comments in the thread linked above.