Raise exception if Active Storage is configured and config.active_storage.service is not explicitly set

[ghousemohamed]

Summary

If config.active_storage.service has not been explicitly set in the respective environment's configuration file, then trying to use active storage throws a vague error message, which makes it harder to debug. This was the following error I had gotten:

Failed to replace attachments_attachments because one or more of the new records could not be saved.

Turned out I had forgotten to explicitly specify config.active_storage.service in my configuration file. Specifying it resolved the issue.

I had spent a considerable amount of time trying to debug this, and I would have immediately known what the fix was if the error message had been clearer. So, I'm turning in this PR so that anyone facing this in the future will know what to do at a quick glance.

Thanks 😁!

Other Information

[ghiculescu]

Hmm, based on the failing tests, it might be better if this error is raised when Active Storage is used. Currently this will raise on any Rails app that has Active Storage loaded (which it does by default) but doesn't have the config, even if it never actually uses AS.

[jorgemanrubia]

Thanks @ghousemohamed, we'll get this merged.

[jorgemanrubia]

@ghousemohamed could you please solve the merge conflicts here?

[ghousemohamed]

@jorgemanrubia I've resolved the merge conflicts

[jorgemanrubia]

@ghousemohamed thanks for sorting those out. A last request: could you add an entry to activestorage/CHANGELOG.md for the change 🙏?

[ghousemohamed]

@ghousemohamed thanks for sorting those out. A last request: could you add an entry to activestorage/CHANGELOG.md for the change 🙏?

@jorgemanrubia Done

[jorgemanrubia]

Thanks @ghousemohamed. This is good to merge @jeremy 🙏

[jeremy]

Nice. Thanks @ghousemohamed!