findDumpsByUrl(url: string,requestingUserId?: string,limit?: number): DumpUrlMatch[]
Returns the dumps requestingUserId may see that were posted with the same
link as url, newest first, for the create form's duplicate notice
(GET /api/dumps?url=). Links are compared in their canonical form, so
tracking parameters, the scheme, www. or a YouTube share format don't hide
a repost.