XF2 Addons Search Improvements 2.17.4

A collection of improvements to XF's Enhanced Search and some for XenForo's default MySQL search

• Adjust defaults for autocomplete boosts to better favor exact matches.
  • Affects non-default "Tag/Username auto-complete search field boosts" option

• Improve handling of expired search links to return a 404 if any errors exist with the arguments as this stops google search indexer from complaining about the previous 400 error code

• For XF2.3.4+, check "View server information" admin permission when viewing elasticsearch statistics

• 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

• 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

• Restore XF2.1 support
• XF2.3 support
• Fix "[E_DEPRECATED] Use of "parent" in callables is deprecated" on search