Description

using our own DEM service on mapserver to serve BIL data for elevation (cf #6579), so far it works fine.

we're in the process of upgrading mapserver to 8.0 and now (cf MapServer/MapServer#6012) by default it enforces the (already required by the WMS specification ?) STYLES parameter, which isnt sent by mapstore 2021.02.

sample query sent by mapstore:
/mnt?SERVICE=WMS&REQUEST=GetMap&layers=mnt_raw&version=1.3.0&bbox=4.2173767089843865,43.240814208984375,4.395904 541015629,43.419342041015625&crs=CRS:84&srs=CRS:84&format=image/bil&width=65&height=65

after a quick look at the code in 2021.02, there was https://github.com/geosolutions-it/MapStore2/blob/2022.01.xx/web/client/utils/cesium/BILTerrainProvider.js#L563 which could have been modified to send an empty &styles=, but it was removed/lost in 68ef691 - now i think the right place to add the missing param should be https://github.com/geosolutions-it/MapStore2/blob/master/web/client/utils/cesium/GeoServerBILTerrainProvider.js#L207 - @allyoucanmap does this make sense to you ?

Expected Result

mapstore should send the mandatory STYLES parameter

Current Result

mapserver returns

msWMSLoadGetMapParams(): WMS server error. Missing required parameter STYLES.
Note to service administrators: defining the "wms_allow_getmap_without_styles" "true" MAP.WEB.METADATA item will disable this check
(backward compatibility with behaviour of MapServer < 8.0)

Other useful information

interoperability is hard.