Don't load app for dav requests

[kesselb]

After #124 it's not longer necessary to add a mapping kdbx => application/x-kdbx to mimetypemapping.json. Instead the keeweb app is loaded for every request and adds the mapping.

Loading the app for every request is not ideal. Recently @sndrr pointed me to dicomviewer app and how they solved that problem. The app automatically appends the mapping for the mime types to mimetypemapping.json and the admins don't have to deal with json. This PR will add the same for keeweb app. Kudos to @ayselafsar for the idea 🚀.

cc @maurerle @SimJoSt mind to help me testing? ;)

[SimJoSt]

@kesselb so when installing this version of the app, it should automatically add the mimetype to the config files, correct?
I see there is an unregister method. When does that one trigger?

What should happen when there is already an entry for the mimetype in the config?

[kesselb]

Suggested change

	if (json_last_error() === JSON_ERROR_NONE) {
	if (json_last_error() === JSON_ERROR_NONE && is_array($existingMapping)) {

otherwise array_merge logs a warning and returns null.

[kesselb]

Thanks @SimJoSt 👍

installing this version of the app, it should automatically add the mimetype to the config files, correct?

Yes. The mapping will be added to $configDirectory/mimetypemapping.json.

I see there is an unregister method. When does that one trigger?

If the app is disabled (either via the app manager or on upgrade if the app is not compatible).

What should happen when there is already an entry for the mimetype in the config?

<?php

$old = [
    'dng' => ["image/x-dcraw"],
    'fb2' => ["application/x-fictionbook+xml", "text/plain"],
    'ical' => ["text/calendar"],
    'kdbx' => ['application/x-kdbx'],
];

$new = [
    'kdbx' => ['application/x-kdbx']
];

var_dump(array_merge($old, $new));

The expected result is to see the entry for kdbx once. That should array_merge already do.

[maurerle]

I just tested this in a development environment with NC18 in docker and can confirm that the registration and unregistration is working properly.

[maurerle]

I don't quite like the way this is done in general. Every app which can open a file with a given mimetype has its own implementation for the (un)registration of a MimeType.
This is a lot of duplication and slightly different code for the same functionality. It does not feel right that an App rewrites the global mimetypemapping file on its own and can possibly break it.

I would like it far better if the core server provided a maintained functionality with a recommended usage to (un)register and mimetypes by just providing the needed mapping.

[arnowelzel]

I don't quite like the way this is done in general. Every app which can open a file with a given mimetype has its own implementation for the (un)registration of a MimeType.
This is a lot of duplication and slightly different code for the same functionality. It does not feel right that an App rewrites the global mimetypemapping file on its own and can possibly break it.

I would like it far better if the core server provided a maintained functionality with a recommended usage to (un)register and mimetypes by just providing the needed mapping.

Unfortunately this is still not solved. Also see nextcloud/server#9192

[arnowelzel]

@jhass To me this looks fine. I'd like to include this for the NC 19 update as well, what do you think?

[jhass]

Your call, this is exactly the kind of thingies I'm a bit tired off to be honest :P