Do not simply take latest UUID from Rekor

[azeemshaikh38]

This line needs better logic to find the right UUID from the list of returned UUIDs.

[spencerschrock]

Note: The https://rekor.sigstore.dev/api/v1/index/retrieve endpoint is experimental and marked as deprecated.
sigstore/rekor#1021

So we should look into changes to our code here:

scorecard-webapp/app/server/post_results.go

Lines 262 to 269 in b012970

	uuids, err := getUUIDsByPayload(ctx, payload)
	if err != nil || len(uuids) == 0 {
	return nil, fmt.Errorf("error finding tlog entries corresponding to payload: %w", err)
	}
	// TODO(#135): We can't simply take the latest UUID. Either:
	// (a) iterate through all returned UUIDs to find the right one.
	// (b) send tlog index in the POST payload to identify the corresponding UUID.
	uuid := uuids[len(uuids)-1] // ignore past entries.