Search Improvements (OS/ES support)

[patrick-austin]

Covers a variety of improvements to free text search functionality.
Closes #267

Changes to functionality

• Expanded the number of fields that are indexed and searchable across various entities
• Metadata from a search comes directly from Lucene, rather than returning a list of ids that then require a subsequent DB call.
  • In addition to performing authorisation on the main returned entity (Investigation/Dataset/Datafile), we also use the public steps/tables to safely return nested information (such as a DatafileParameter without additional time spent authorising)
• Support for faceting of results, sorting, searching after, flexible batches of search results
• Support for other search engines, specifically Opensearch/Elasticsearch
  • Note that a branch without the Opensearch code but all the other features exists

Changes to code

• Various entities have had getDoc either added or expanded, alongside the addition of getDocumentFields which enforces that the search component does not return metadata that isn't allowed by the ICAT public steps/tables
• Modified existing search functions in ICATRest and added new endpoints search/documents and facet/documents
• Changes to EntityBeanManager to support new search calls
• Small additions to GateKeeper to allow the publicly allowed search fields to be marked as stale and updated as public steps/tables are updated
• Changes to PropertyHandler to support different SearchEngines as config options as well as other new config parameters
• LuceneManager replaced with generic SearchManager which interacts with the search engine via an instance of SearchApi
• Creation of SearchApi, and abstract class for interfacing with search engine implementations
• LuceneApi modified extensively, and now extends SearchApi
• Creation of OpensearchApi which extends SearchApi and supports either Opensearch or Elasticsearch clusters by building generic JSON. Also has some static functionality refactored into supporting classes:
  • OpensearchQueryBuilder
  • OpensearchScriptBuilder
• Creation of FacetDimension and FacetLabel to represent facets of results, and replacing LuceneSearchResult with SearchResult which has facet support
• Various small changes to rename variables from luceneAbc to searchAbc to reflect what is or isn't specific to the icat.lucene search engine
• Updated tests

Interdependencies on other components

• 19 unit conversion icat.utils#20
• Search improvements icat.client#33
• 18 search improvements icat.lucene#27

[VKTB]

I will continue reviewing the rest of the changes after I re-review the changes you have made in the icat.lucene PR.

[VKTB]

@patrick-austin I have finished reviewing this PR so feel free to start addressing and pushing changes. Let me know when you are done and I will review your changes.

[VKTB]

Looking much nicer, thanks for making the changes. Just a few docstring related comments which once address will make this PR ready to be merged.