[DS-2160] [DS-2187] Remove non-nested usages of DSIndexer and some ea…

…sy non-nested usages of DSQuery

DSIndexer dependency (outside org.dspace.search) removal: (complete)
====
Removed (unused) java class import from MediaFilter
Removed ItemImport DSIndexer.setBatchProcessingMode references, removed java class import
Removed FlyWay allback to DatabaseLegacyReindexer, removed DatabaseLegacyReindexer class

DSQuery dependency (outside org.dspace.search) removal: (WIP)
====
Removed org.dspace.app.webui.search.LuceneRequestProcessor and dependencies/imports in:
 - its reference in dspace.cfg, JSPUI Discovery section, updated comments to reflect removal
 - (unused) class import in org.dspace.app.webui.servlet.AdvancedSearchServlet
 - (unused) class import in org.dspace.app.webui.servlet.OpenSearchServlet
 - (unused) class import in org.dspace.app.webui.servlet.SimpleSearchServlet
 - (unused) class import in org.dspace.app.webui.servlet.admin.ItemMapServlet

Removed org.dspace.xmlui.aspect.adminstrative.mapper.LuceneSearchRequestProcessor and its reference in dspace.cfg, XMLUI Discovery section, updated comments to reflect removal.

Notes: org.dspace.app.webui.search now only contains SearchRequestProcessor and
SearchProcessorException. SearchReqeuestProcessor is now only implemented by
org.dspace.app.webui.discovery.DiscoverySearchRequestProcessor. Would it make sense to move
these classes into org.dspace.app.webui.discovery and refactor references to
SearchProcessorException accordingly? Or is it safer for unknown customisations to leave as
is?

org.dspace.app.xmlui.opensearch.DiscoveryOpenSearchGenerator and
org.dspace.app.xmlui.opensearch.StandardOpenSearchGenerator had their summary comments mixed
up - I swapped these back around. No removal of StandardOpenSearchGenerator yet, needs closer
inspection of usage in sitemap, pattern mapping etc.

dspace-xmlui/src/main/java/org/dspace/app/xmlui/opensearch/DiscoveryOpenSearchGenerator.java

@@ -37,7 +37,8 @@
  * Generate an OpenSearch compliant search results document for DSpace, either scoped by a collection,
  * a community or the whole repository.
  *
- * This class implements the generate() method in order to issue a search using the PostgreSQL indexes.
+ * This class implements the generate() method in order to issue a search using the Discovery search service
+ * (Solr based search)
  * Search params are parsed by AbstractOpenSearchGenerator class.
 
  * I18N: Feed's are internationalized, meaning that they may contain references

dspace-xmlui/src/main/java/org/dspace/app/xmlui/opensearch/StandardOpenSearchGenerator.java

@@ -33,10 +33,9 @@
  * Generate an OpenSearch compliant search results document for DSpace, either scoped by a collection,
  * a community or the whole repository.
  *
- * This class implements the generate() method in order to issue a search using the Discovery search service
- * (Solr based search)
+ * This class implements the generate() method in order to issue a search using the PostgreSQL indexes.
  * Search params are parsed by AbstractOpenSearchGenerator class.
-
+ *
  * I18N: Feed's are internationalized, meaning that they may contain references
  * to messages contained in the global messages.xml file using cocoon's i18n
  * schema. However the library used to build the feeds does not understand

dspace/config/dspace.cfg

@@ -1306,22 +1306,18 @@ recent.submissions.count = 0
 #        org.dspace.app.webui.components.CollectionItemList
 
 #### JSPUI Discovery (extra Discovery setting that applies only to JSPUI) ####
-# uncomment the following configuration if you want to restore the legacy Lucene
-# search provider with JSPUI (be sure to re-enable also the search consumer)
-# plugin.single.org.dspace.app.webui.search.SearchRequestProcessor = \
-#		org.dspace.app.webui.search.LuceneSearchRequestProcessor
-#
-# default since DSpace 4.0 is to use the Discovery search provider
+# The legacy JSPUI Lucene search provider deprecated in DSpace 4.0
+# (org.dspace.app.webui.search.LuceneSearchRequestProcessor) has been removed
+# in DSpace 6.0.
+# The default since DSpace 4.0 is to use the Discovery search provider
 plugin.single.org.dspace.app.webui.search.SearchRequestProcessor = \
 		org.dspace.app.webui.discovery.DiscoverySearchRequestProcessor
 
 #### XMLUI Discovery (extra Discovery setting that applies only to XMLUI) ####
-# uncomment the following configuration if you want to restore the legacy Lucene
-# search provider with XMLUI (be sure to re-enable also the search consumer)
-# plugin.single.org.dspace.app.xmlui.aspect.administrative.mapper.SearchRequestProcessor = \
-#		org.dspace.app.xmlui.aspect.administrative.mapper.LuceneSearchRequestProcessor
-#
-# default since DSpace 4.0 is to use the Discovery search provider
+# The legacy XMLUI Lucene search provider deprecated in DSpace 4.0
+# (org.dspace.app.xmlui.aspect.administrative.mapper.LuceneSearchRequestProcessor)
+# has been removed in DSpace 6.0.
+# The default since DSpace 4.0 is to use the Discovery search provider
 plugin.single.org.dspace.app.xmlui.aspect.administrative.mapper.SearchRequestProcessor = \
 		org.dspace.app.xmlui.aspect.administrative.mapper.DiscoverySearchRequestProcessor