notification manager deterministic app call order

[gavine99]

Summary

Changes to allow a deterministic calling order of notification apps by the notification manager.

More detail

The notification manager will always call notify() on the 'main' notifications app before other notification apps.
The notification manager will always call markProcessed() , count() and flush() on other notifications apps before calling it on the 'main' notification app.

Reason for change

I have built, and others might build, notification apps that depend on the 'main' notification app and, therefore, require a definitive calling order by the notification manager.

No internal or external api changes.
No new tests required. no current tests changed.
No front-end changes.
No documentation updates required.
No backporting required.

[artonge]

Looks good to me

[come-nc]

@gavine99 Can you run composer run cs:fix to fix the code style please?

[nickvergessen]

I fixed CI and squashed the commits, I hope you don't mind.

[artonge]

Good to force merge I think.

[welcome]

Thanks for your first pull request and welcome to the community! Feel free to keep them coming! If you are looking for issues to tackle then have a look at this selection: https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22

[github-actions]

Hello there,
Thank you so much for taking the time and effort to create a pull request to our Nextcloud project.

We hope that the review process is going smooth and is helpful for you. We want to ensure your pull request is reviewed to your satisfaction. If you have a moment, our community management team would very much appreciate your feedback on your experience with this PR review process.

Your feedback is valuable to us as we continuously strive to improve our community developer experience. Please take a moment to complete our short survey by clicking on the following link: https://cloud.nextcloud.com/apps/forms/s/i9Ago4EQRZ7TWxjfmeEpPkf6

Thank you for contributing to Nextcloud and we hope to hear from you soon!

(If you believe you should not receive this message, you can add yourself to the blocklist.)