Further Fixes for STAC Search (#2340)

* Fix STAC search endpoint reference

This mistakenly used double slashes in the URL
which would break the output. A single slash fixes
this.

Closes #2354

* Assets should be dict, not list

As specified in the STAC spec: https://stacspec.org/en/about/stac-spec/
assets are dicts, not lists. When missing,
now they are initialized as the correct empty
data structures.

Closes #2354

* Correctly initialize temporal instant

Previously the `datetime` field was not used to initalize
the temporal instant, causing it to be overridden by
other approximations.

This ensure that the initialization happens correctly,
and the overrides only occur in cases when `datetime`
is None.

Closes #2356

Author: rajadain

pygeoapi/api/stac.py

@@ -284,7 +284,7 @@ def landing_page(api: API,
         'rel': 'search',
         'type': FORMAT_TYPES[F_JSON],
         'title': l10n.translate('STAC API search', request.locale),
-        'href': f"{api.base_url}/stac-api//search?f={F_JSON}"
+        'href': f"{api.base_url}/stac-api/search?f={F_JSON}"
     }]
 
     return headers, status, to_json(content, api.pretty_print)
@@ -379,9 +379,11 @@ def search(api: API, request: Union[APIRequest, Any]) -> Tuple[dict, int, str]:
                     geom = from_geojson(json.dumps(feature['geometry']))
                     feature['bbox'] = geom.bounds
 
-                for la in ['links', 'assets']:
-                    if feature.get(la) is None:
-                        feature[la] = []
+                if feature.get('links') is None:
+                    feature['links'] = []
+
+                if feature.get('assets') is None:
+                    feature['assets'] = {}
 
     stac_api_response['numberReturned'] = len(stac_api_response['features'])
 
@@ -488,18 +490,20 @@ def get_temporal(feature: dict) -> dict:
     if datetime_ is None and None not in [start_datetime, end_datetime]:
         LOGGER.debug('Temporal range partially exists')
     elif datetime_ is not None:
+        value['datetime'] = datetime_
         LOGGER.debug('Temporal instant exists')
 
     LOGGER.debug('Attempting to derive temporal from GeoJSON feature')
     LOGGER.debug(feature)
-    if feature.get('time') is not None:
+    if value.get('datetime') is None and feature.get('time') is not None:
         if feature['time'].get('timestamp') is not None:
             value['datetime'] = feature['time']['timestamp']
         if feature['time'].get('interval') is not None:
             value['start_datetime'] = feature['time']['interval'][0]
             value['end_datetime'] = feature['time']['interval'][1]
 
-    if feature['properties'].get('created') is not None:
+    if value.get('datetime') is None \
+       and feature['properties'].get('created') is not None:
         value['datetime'] = feature['properties']['created']
 
     if not value: