Clarify the convenience parameters that servers need to implement and the correspondence with more general parameters

[jerstlouis]

From #185

8 - It looks like subset=Lat(40:50),Lon(10:20) and bbox=... parameters do the same thing. Why does the API specify two ways for doing the same thing? Same seems to apply for time.

Correct. bbox and datetime are basically a convenience around the more powerful and explicit subset parameter (which is the only one that supports additional dimensions). These convenience parameters are also more familiar to users of WMS and OGC API - Features. This is particularly convenient if you want to tweak request URLs to return /map vs. /items and /map vs. /coverage for the same collection.

Considering that a lot more clients are being developed than servers, and that OGC APIs are intended for users to play with directly in their browser, requiring both option from the server introduces a very small burden for server implementors (who can simply map both syntaxes to their implementation), while providing the flexibility for clients and users to pick their favorite options.

[jerstlouis]

SWG 2025-05-07:

Editing actions:

• Clarify that the optional requirement classes of OGC API - Coverages define general subsetting parameters (subset and subset-crs), as well as convenience subsetting parmeters mapping directly to those more general subsetting parameters (bbox, bbox-crs and datetime). Explain how users from specific communities or with experience using a particular legacy WxS service find one or the other option for convenient/familiar.
• Explain clearly how the convenience parameters map to the general subsetting parameters, to facilitate the implementations of both in servers which can easily map the convenience parameters to the same underlying functionality as the general ones.