[Xon] Search Improvements 2.17.1

• Fix when logging debugging for some search queries would throw unexpectedly

• Enhanced specialized search with additional debug capabilities
• Update specialized search to support SearchOrder type
• Fix XF2.1 when using specialized search functionality (aka fix tag/user autocomplete with XF2.1)

• Improve 3rd party support for specialized search index support

• Add additional hookpoints for customizing "specialized search indexer" functionality
• On search results page, when searching a conversation(XF2.2)/direct message(XF2.3) display "with conversation/direct message"

• Search extensions API changes for better XF compatibility, required for Conversation Improvements/Essentials
  • XF2.3 compatibility fix for custom "SearchOrder" class
  • Simplify asSqlConstraint code (expected to always return an array)
  • AbstractConstraint::setMatchType needs to normalize to an int for MetadataConstraint::matchType

• Update installer to verify ElasticSearch index does not require rebuilding when this add-on is installed/updated/rebuilt
• Return 400 status code instead of 200 when the search query is wrong

• Compatibility fix for Username auto-complete using XFES and Tag auto-complete using XFES add-ons

• Fix min/max range searches (ie word-count) where flipped when using MySQL full-text search

• Fix guest user searches could be sent into a redirect loop depending on search criteria

• Fix XF2.3.0 infinite search redirect for guests