API for file details

[tobiasKaminsky]

For nextcloud/android#795 we need to have an API which accepts a fileID and returns informations of this file, specifically the remote path for the specific user.

Background: Android client currently does not store a file list so we do not know where a shared file is for a specific user.

[MorrisJobke]

cc @icewind1991 @rullzer @nickvergessen

[rullzer]

@icewind1991 can we somehow reuse the webdav search API for this?

[nickvergessen]

Currently the file id can only be selected: {http://owncloud.org/ns}id

server/apps/dav/lib/Files/FileSearchBackend.php

Line 131 in e392d02

new SearchPropertyDefinition(FilesPlugin::FILEID_PROPERTYNAME, false, true, false, SearchPropertyDefinition::DATATYPE_NONNEGATIVE_INTEGER),

But the searchable flag is false.

[icewind1991]

#4222 adds searching by fileid