Honor "Content-Type" headers in PROPFIND requests

[jwodder]

• If a PROPFIND request lacks a Content-Type, treat it as text/xml

• If a PROPFIND request has a Content-Type of either text/xml or application/xml, use the charset parameter (if any) when decoding the request body (cf. [1])

  • To do: Look into whether there's a registered MIME type for WebDAV XML
    • https://www.iana.org/assignments/media-types/media-types.xhtml does not seem to list any MIME types that mention WebDAV (other than application/davmount+xml, which doesn't apply here).

• If a PROPFIND request has any other Content-Type, reject the request