THREDDS 5.x: Add support for palettes returned by THREDDS GetMetadata call

[sppigot]

At the moment TerriaJS correctly reads the available styles that can be used with a THREDDS WMS layer from the GetCapabilities document i.e. the <Style> elements embedded in the element. e.g.:

<Style>
     <Name>raster/default</Name>
     <Title>raster/default</Title>
     <Abstract>raster style, using the default palette. Available palettes can be found in the response to https://thredds.roam.im:443/thredds/wms/roam/292/breakertypes-reprojected.nc?request=GetMetadata&item=layerDetails&layerName=H_mean </Abstract>
     <LegendURL width="110" height="264">
       <Format>image/png</Format>
       <OnlineResource xlink:type="simple" xlink:href="https://thredds.roam.im:443/thredds/wms/roam/292/breakertypes-reprojected.nc?REQUEST=GetLegendGraphic&PALETTE=default&LAYERS=H_mean&STYLES=raster/default"/>
     </LegendURL>
</Style>

These styles appear as a drop down in the Layer info displayed in the workbench:

However the GetLegendGraphic URLs included in the <Style> elements specify the PALETTE as default. This means TerriaJS can only use the default palette to colour a THREDDS layer.

But the <Style> element also provides info on how to retrieve the list of palettes that can be used to style the layer. This is a THREDDS specific GetMetadata call (which conveniently returns JSON):

e.g. https://thredds.roam.im:443/thredds/wms/roam/292/breakertypes-reprojected.nc?request=GetMetadata&item=layerDetails&layerName=H_mean

Which returns:

{
    "scaleRange": [
        -50,
        50
    ],
    "categorical": false,
    "belowMinColor": "extend",
    "noDataColor": "extend",
    "downloadable": true,
    "datesWithData": {"2023": {"7": [
        3,
        4,
        5
    ]}},
    "continuousT": false,
    "bbox": [
        150.77268981933594,
        -22.654677426260164,
        150.80520629882812,
        -22.62298249999918
    ],
    "supportsProfiles": false,
    "palettes": [
        "default",
        "default-inv",
        "div-BrBG",
        "div-BrBG-inv",
        "div-BuRd",
        "div-BuRd-inv",
        "div-BuRd2",
        "div-BuRd2-inv",
        "div-PRGn",
        "div-PRGn-inv",
        "div-PiYG",
        "div-PiYG-inv",
        "div-PuOr",
        "div-PuOr-inv",
        "div-RdBu",
        "div-RdBu-inv",
        "div-RdGy",
        "div-RdGy-inv",
        "div-RdYlBu",
        "div-RdYlBu-inv",
        "div-RdYlGn",
        "div-RdYlGn-inv",
        "div-Spectral",
        "div-Spectral-inv",
        "psu-inferno",
        "psu-inferno-inv",
        "psu-magma",
        "psu-magma-inv",
        "psu-plasma",
        "psu-plasma-inv",
        "psu-viridis",
        "psu-viridis-inv",
        "seq-BkBu",
        "seq-BkBu-inv",
        "seq-BkGn",
        "seq-BkGn-inv",
        "seq-BkRd",
        "seq-BkRd-inv",
        "seq-BkYl",
        "seq-BkYl-inv",
        "seq-BlueHeat",
        "seq-BlueHeat-inv",
        "seq-Blues",
        "seq-Blues-inv",
        "seq-BuGn",
        "seq-BuGn-inv",
        "seq-BuPu",
        "seq-BuPu-inv",
        "seq-BuYl",
        "seq-BuYl-inv",
        "seq-GnBu",
        "seq-GnBu-inv",
        "seq-Greens",
        "seq-Greens-inv",
        "seq-Greys",
        "seq-Greys-inv",
        "seq-GreysRev",
        "seq-GreysRev-inv",
        "seq-Heat",
        "seq-Heat-inv",
        "seq-OrRd",
        "seq-OrRd-inv",
        "seq-Oranges",
        "seq-Oranges-inv",
        "seq-PuBu",
        "seq-PuBu-inv",
        "seq-PuBuGn",
        "seq-PuBuGn-inv",
        "seq-PuRd",
        "seq-PuRd-inv",
        "seq-Purples",
        "seq-Purples-inv",
        "seq-RdPu",
        "seq-RdPu-inv",
        "seq-Reds",
        "seq-Reds-inv",
        "seq-YlGn",
        "seq-YlGn-inv",
        "seq-YlGnBu",
        "seq-YlGnBu-inv",
        "seq-YlOrBr",
        "seq-YlOrBr-inv",
        "seq-YlOrRd",
        "seq-YlOrRd-inv",
        "seq-cubeYF",
        "seq-cubeYF-inv",
        "x-Ncview",
        "x-Ncview-inv",
        "x-Occam",
        "x-Occam-inv",
        "x-Rainbow",
        "x-Rainbow-inv",
        "x-Sst",
        "x-Sst-inv"
    ],
    "units": "m",
    "numColorBands": 250,
    "supportedStyles": [
        "default-scalar",
        "colored_contours",
        "contours",
        "raster"
    ],
    "timeAxisUnits": "ISO8601",
    "defaultPalette": "x-Rainbow",
    "queryable": true,
    "supportsTimeseries": true,
    "nearestTimeIso": "2023-08-05T11:00:00.000Z",
    "aboveMaxColor": "extend",
    "noPaletteStyles": ["contours"],
    "supportsTransects": true,
    "logScaling": false
}

Included in this information is a 'defaultPalette' key that the THREDDS admin can set for the layer.

It would be great if:

• the list of Palettes returned by this call could be displayed as a drop down in the workbench labelled as 'Palettes:'
• TerriaJS would respect the 'defaultPalette' and 'scaleRange' information returned by the GetMetadata call. (As regards 'scaleRange', this information needs to be specified in the TerriaJS catalog item using 'colorScaleMinimum' and 'colorScaleMaximum' and our THREDDS server might not be respecting our rules for this, however TerriaJS should be able to use whatever GetMetadata returns)

[nf-s]

I believe this is a duplicate of

• Allow users to select color palette on ncWMS2 endpoints #2200

[AnaBelgun]

Check "model dimensions" in github repo to see examples of selectable multiple dimensions

[sixlighthouses]

Draft PR
#7059