openapi: synchronized subset parameter with Maps

- Allow use of single `*` for time instant
- Make support for `*` optional for non-temporal dimensions
 (the concept of minimum/maximum value is confusing for geographic longitude wrapping around in particular,
 with different conventions like 0..360 degrees and -180..180 degrees)

standard/openapi/ogcapi-coverages-1.bundled.json

@@ -3133,7 +3133,7 @@
       "subset": {
         "name": "subset",
         "in": "query",
-        "description": "Retrieve only part of the data by slicing or trimming along one or more axis\nFor trimming: {axisAbbrev}({low}:{high}) (preserves dimensionality)\n   An asterisk (`*`) can be used instead of {low} or {high} to indicate the minimum/maximum value.\nFor slicing:  {axisAbbrev}({value})      (reduces dimensionality)\n",
+        "description": "Retrieve only part of the data by slicing or trimming along one or more axis\nFor trimming: {axisAbbrev}({low}:{high}) (preserves dimensionality)\nFor slicing:  {axisAbbrev}({value})      (reduces dimensionality)\nAn asterisk (`*`) can be used instead of {low} or {high} to indicate the minimum/maximum value.\nFor a temporal dimension, a single asterisk can be used to indicate the high value.\nSupport for `*` is required for time, but optional for spatial and other dimensions.\n",
         "style": "form",
         "explode": false,
         "required": false,

standard/openapi/parameters/coverages-core/subset.yaml

@@ -3,8 +3,10 @@ in: query
 description: |
    Retrieve only part of the data by slicing or trimming along one or more axis
    For trimming: {axisAbbrev}({low}:{high}) (preserves dimensionality)
-      An asterisk (`*`) can be used instead of {low} or {high} to indicate the minimum/maximum value.
    For slicing:  {axisAbbrev}({value})      (reduces dimensionality)
+   An asterisk (`*`) can be used instead of {low} or {high} to indicate the minimum/maximum value.
+   For a temporal dimension, a single asterisk can be used to indicate the high value.
+   Support for `*` is required for time, but optional for spatial and other dimensions.
 style: form
 explode: false
 required: false