add items link to collection (geopython#877)

* add items link to collection, improves geopython#876

* update title text

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Co-authored-by: Genuchten <paul.vangenuchten@wur.nl>
Co-authored-by: Tom Kralidis <tomkralidis@gmail.com>

pycsw/ogc/api/records.py

@@ -457,6 +457,18 @@ def collection(self, headers_, args, collection='metadata:main'):
             'title': 'This document as HTML',
             'href': f"{url_base}?f=html",
             'hreflang': self.config['server']['language']
+        }, {
+            'rel': 'items',
+            'type': 'application/json',
+            'title': 'items as GeoJSON',
+            'href': f"{url_base}/items?f=json",
+            'hreflang': self.config['server']['language']
+        }, {
+            'rel': 'items',
+            'type': 'text/html',
+            'title': 'items as HTML',
+            'href': f"{url_base}/items?f=html",
+            'hreflang': self.config['server']['language']
         }, {
             'rel': 'http://www.opengis.net/def/rel/ogc/1.0/queryables',
             'type': 'application/schema+json',