Use GeoServer's minimum and maximum image generation width and height for serialized width and height inputs

[prushforth]

Background

When generating a \ for an image-based map, the current MapML extension serializes two \s which reflect the standard width and height WMS parameter values. Such inputs are serialized to support GetMap and GetFeatureInfo request templates, and (currently) have hard-coded min and max attribute values:

...
    <map-extent  units="OSMTILE">
      <map-input name="z" type="zoom"  min="0" max="18"/>
      <map-input name="xmin" type="location" rel="map" position="top-left" axis="easting" units="pcrs" min="1.6011619366020126E7" max="1.6528622369542673E7"/>
      <map-input name="ymin" type="location" rel="map" position="bottom-left" axis="northing" units="pcrs" min="-5411138.5986247435" max="-4804213.1199940005"/>
      <map-input name="xmax" type="location" rel="map" position="top-right" axis="easting" units="pcrs" min="1.6011619366020126E7" max="1.6528622369542673E7"/>
      <map-input name="ymax" type="location" rel="map" position="top-left" axis="northing" units="pcrs" min="-5411138.5986247435" max="-4804213.1199940005"/>
      <map-input name="w" type="width" min="1" max="10000"/>
      <map-input name="h" type="height" min="1" max="10000"/>
      <!-- If the layer is queryable per the GeoServer catalog, a query link template and associated variables should be serialized -->
      <map-link  rel="image" tref="http://example.org/geoserver/wms?request=GetMap&crs=EPSG:3857&service=WMS&bbox={xmin},{ymin},{xmax},{ymax}&layers=tasmania_state_boundaries&styles=green&format=image/png&width={w}&language=en&version=1.3.0&transparent=true&height={h}"/>
      <map-input name="i" type="location" axis="i" units="map"/>
      <map-input name="j" type="location" axis="j" units="map"/>
      <map-link rel="query" tref="http://example.org/geoserver/wms?request=GetFeatureInfo&query_layers=tasmania_state_boundaries&crs=EPSG:3857&bbox={xmin},{ymin},{xmax},{ymax}&language=en&version=1.3.0&transparent=true&service=WMS&layers=tasmania_state_boundaries&width={w}&x={i}&feature_count=50&y={j}&styles=green&info_format=text/mapml&height={h}"/>
    </map-extent>
...

Requirement

All width and height inputs should be serialized with the min and max attribute values in effect for the GeoServer system, if such limits indeed exist.

(Possible) Reference

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