Introduce OCConnectionRequestMethodREPORT to apply oc:filter-rules on DAV requests

[SamuAlfageme]

See description for the REPORT method on https://tools.ietf.org/html/rfc3253#section-3.6

Unlike a resource property, which has a single value, the value of a report can depend on additional information specified in the REPORT request body and in the REPORT request headers.

Some examples we have in ownCloud for this kind of "additional information" are:

Fetch all the user favorites:

<oc:filter-files  xmlns:d="DAV:" xmlns:oc="http://owncloud.org/ns">
    <d:prop>
        <!-- the properties you want to include on the REPORT -->
    </d:prop>
    <oc:filter-rules>
        <oc:favorite>1</oc:favorite>
    </oc:filter-rules>
</oc:filter-files>

Get the files tagged with a Collaborative Tag:

Replace the content of oc:filter-rules above with:

<oc:systemtag>{{ID of the collaborative tag}}</oc:systemtag>

In the future, REPORT might also be adopted for search (ref. owncloud/core#25373)

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There's some documentation for this on https://github.com/owncloud/documentation/issues/2950 (specially everything rel. to pagination)

[SamuAlfageme]

In the future, REPORT might also be adopted for search (ref. owncloud/core#25373)

Update: owncloud/core#25373 (comment)

[felix-schwarz]

This is implemented by the SDK at the time of writing.