ngl_segments needs to be able to expand flywire URLs

[jefferis]

See

https://github.com/jefferis/fafbseg/blob/9bd4bd990a4c89da54c763d88efb1bbd808b8b7d/R/ids.R#L95

The problem is that they will normally need to be expanded from flywire short form (the default) to long form (like other neuroglancer instances use)

e.g. from

short="https://ngl.flywire.ai/?json_url=https://globalv1.flywire-daf.com/nglstate/5747205470158848"

to

https://ngl.flywire.ai/#!%7B%22layers%22:%5B%7B%22source%22:%22precomputed://gs://microns-seunglab/drosophila_v0/alignment/image_rechunked%22%2C%22type%22:%22image%22%2C%22blend%22:%22default%22%2C%22shaderControls%22:%7B%7D%2C%22name%22:%22Production-image%22%7D%2C%7B%22tab%22:%22graph%22%2C%22source%22:%22graphene://https://prodv1.flywire-daf.com/segmentation/1.0/fly_v31%22%2C%22type%22:%22segmentation_with_graph%22%2C%22selectedAlpha%22:0.62%2C%22colorSeed%22:1358768360%2C%22segments%22:%5B%22720575940619527173%22%2C%22720575940628130268%22%2C%22720575940630484179%22%5D%2C%22hiddenSegments%22:%5B%22720575940634222734%22%2C%22720575940636364870%22%5D%2C%22skeletonRendering%22:%7B%22mode2d%22:%22lines_and_points%22%2C%22mode3d%22:%22lines%22%7D%2C%22graphOperationMarker%22:%5B%7B%22annotations%22:%5B%5D%2C%22tags%22:%5B%5D%7D%2C%7B%22annotations%22:%5B%5D%2C%22tags%22:%5B%5D%7D%5D%2C%22pathFinder%22:%7B%22color%22:%22#ffff00%22%2C%22pathObject%22:%7B%22annotationPath%22:%7B%22annotations%22:%5B%5D%2C%22tags%22:%5B%5D%7D%2C%22hasPath%22:false%7D%7D%2C%22name%22:%22Production-segmentation_with_graph%22%7D%5D%2C%22navigation%22:%7B%22pose%22:%7B%22position%22:%7B%22voxelSize%22:%5B4%2C4%2C40%5D%2C%22voxelCoordinates%22:%5B115198%2C55453%2C1537%5D%7D%7D%2C%22zoomFactor%22:4.145162302892657%7D%2C%22perspectiveOrientation%22:%5B-0.22566604614257812%2C-0.034010399132966995%2C-0.07959923148155212%2C0.97035151720047%5D%2C%22perspectiveZoom%22:4888.123757966904%2C%22showSlices%22:false%2C%22jsonStateServer%22:%22https://globalv1.flywire-daf.com/nglstate/post%22%2C%22selectedLayer%22:%7B%22layer%22:%22Production-segmentation_with_graph%22%2C%22visible%22:true%7D%2C%22layout%22:%22xy-3d%22%7D

This requires an authenticated all to the flywire server. I have some code that already does this in #15 (see https://github.com/jefferis/fafbseg/blob/2dc800ff191ace8de5d2ced6997834f6f492457c/R/flywire-fetch.R#L26-L28)